I think what we're seeing is dual fold ; a massive shake up of the warhammer world lots of things are consolidated. There's differing opinion on this, but i think they are going to go from X of Chaos, Y of Chaos, Z of Chaos to "Legions of Chaos". Ditton on elves. Ditto on Dead Things. Ditto on Humans. It gets a little trickier with the non-humans. I doubt anything will get squatted, but there are people that disagree with me.
Why the shake up ? I spelled out the economics of it in another thread, but basically, books are extremely costly to produce, hugely man-power intensive, so the less times you have to go to print = better. If you have a rule book, and fifteen army books, that's 16 print "processes" (which include design, writing, editing, layout, proofing, printing, likely multiple passes at each other than printing. Very manpower heavy, therefore costly. Also printing books individually is REALLY very costly).
If you can print the same amount of information in say 1 main rule book, and 5-6 army compendiums, you save a lot of money on costs of producing products that don't generate a ton of margin to begin with. YOu also make it capable of turning revisions of the game more quickly, but most importantly you free up resources to design rules for more models. Rules for which you will eventually release a model. You could theoretically take the Privateer / Infinity model of releases ; release a large book of "elves", with an additional 6 sets of rules for models that don't have models. You then take the next 12-24 months to release those 10 new things (remember, interleaved in taht 12-24 months is also all the other fantasy releases too, and of course, clearly their other products).
What does this do ? Well, it gets people to buy the book for one thing, but it also builds anticipation and buzz for people to come back to your website, etc., to try to find out when the SuperMegaAwesome ElfGuy is being released. Privateer has perfected this model. They drop a book for each game on a rotating annual schedule. Depending on the book it has a handful to about 10 items per army, with a couple mercs thrown in there usually too. That's what's going to come out for whichever game in the next 24 month cycle. So even though each army might only be getting 6 new things, it might be spread over 24 months. Builds anticipation, but also delivers a payload of goodies with the book immediately.
GW's currently model is a blunderbuss effect - New Army Book drops, along with a week or two (or very rarely a 2 phase drop) with all the new toys. And then you hit the blunderbuss reload phase: you get nothing until your book gets updated again. With 15 books, this means that you have a choice ; your lower selling armies you put time and resources into updating (brets, woodies), but it might not be economically viable to update as say, Dark or HIgh elves again.
Consolidation of armies does away with a LOT of this. There's another angle too. Inclusive customer purchasing rather than exclusive.
Wargames have almost always been exclusive in terms of interior customer marketing. I.e. you pick an army or faction in a game and that is your army. It's a relatively recent phenomenon where games are getting inclusive in their interior marketing. What do i mean by this ? It might make more sense if we examine the problem rather than the root cause.
Say you have 1000 total elf players worldwide. 550 play dark elves. 350 play high elves. 100 play woodies. (i am specifically using nice round numbers, and wide spectrum gulfs just to illustrate a point).
You (the company) can tell this roughly by purchasing records of books and models. You want to update Wood Elves, but it has less than 20% of the economic turn potential of Dark Elves. It costs pretty much the same to publish Army Book: Dark Elves, as it does Wood Elves, and costs roughly the same to get models designed and produced. But the pool of potential buyers is drastically smaller.
Exclusive model says: I'm a customer and i have chosen woodies. Company expends the capital to release wood elves book and goodies. Great ! 10% of elf players out there can take advantage, and then you get stragglers who want to paint . own, convert, etc the model.
Inclusive model says: INstead of "only" being able to play a single army, combine up like themes, or allow trans-pollination (trans-pollination example would be "allies" or "mercenaries" in games). If you combine Dark, High, and Wood elves, and then you release a new wood elf looking themed toy, your potential market is now 1000 elf players. You probably won't hit all 1000, but before, your potential market was 100 of 1000 + anomalies. Now your potential market is 1000 of 1000 players + anomalies.
And how'd you do that ? Very simply. Via some writing and (hopefully, though this is
GW...) playtesting, and ultimately a rule book publish (which is a net zero effect, you're doing that anyway one way or another).
So now you have your Host of the Eternity King player who can pick and choose almost freely amongst three product line offerings where he could pick one before. Win ! Great ! Previously Mr. Wood Elf Player was only sampling one product line. Now he can activate and buy and sample 3.
Now add in allies (trans-pollination, or the mixing of unlike things). Give that player the ability to use Ogres in a minor way. Or Lizards. Allow that Legions of Chaos player to take some undead.

Now you have a player who can pick and choose amongst LOTS of lines and activate all over your range.
Part of the problem with fantasy right now (well.... pre-End Times) is that you pick your army and build it. If you're a huge fan of the game you might build a second or third, but honestly, most people are going to stop at 1. Whereas with other games like infinity or
WM, the average sized game makes it relatively easy to play more than one faction. With Fantasy the buy in to start a second army is just too large and daunting for most players. So you have most of your customers for the game locked into one product line and one product line only. And if they have what they need, and aren't buying more, that customer is dead to you for that product line until you release something new for that army.
This does away with that problem, at least potentially. You now have a customer who can spend his money on several base product lines, and possibly even more. Which means that this customer (previously inert for many years at a time), combined with the rolling release schedule, now activates for you several times (hopefully) over a 2 year rolling release. Again, using the "over the next 24 months you'll get 6 new things". Past the initial barrage of purchases our former Just Woody Elf only player can make by opening up High and Dark to him, you also have now potentially allowed him to activate (i.e. buy stuff) for you several times in the next 2 years. You are building what you hope will be a rolling revenue stream with this model.
It's pretty clear that they are taking steps to go from a game that has an interior customer exclusive marketing model, to an interior customer inclusive marketing model. 7th Editions Unbound in
40k can serve as no greater example (perhaps hamfisted, though i have enjoyed it) to this. I think you're going to "compendiums" of armies rather than individual armies which will allow you to (using elves as a model) play Mono-Dark, MOno-High, Mono-Wood .... and then have rules which let you play combined (say like Host of the Eternity King, and etc). I think they will do this so that, with customers they already "have" they will expose those captured customers to potentially new buying habits (i.e. i was a high elf player.... after Khaine, i'm now buying up wood and Dark elves... i'm sure some chaos and undead players are doing the same).
Finally, they are shaking things up, and that's because the game isn't doing well. It's this monolithic juggernaut of books, models, and while very very fun game, its definitely not as fluid as some other games out there. It's also continuing to be a lesser part of their profit portfolio. To use a cliche, Fantasy is a boat that is taking on water, and the crew have been asleep for some time. The first mate might have just woke up though, and there are signs that he definitely SEES the bucket, and might even think that he could pick it up and start putting that wet stuff back into the ocean. His hand might even be outstretched to pick up the bucket.
The game isn't bringing in the money it once did, is a bear to update, and is not attracting new players due to the buy-in and barrier to entry. These are all per
GW corporate statements and releases (albeit condensed).
How do you break barrier to entry ? Reduce buy in. What's 1 really easy way you do that ? Make it *possible* to reduce model cost. They did this. They moved lords and heroes up to 50% of points you can use. This literally is a move to reduce initial buy-in barrier to entry.
How do get existing customers to spend more. Well... release more models, sure. But how do you "do more with less" in this instance ? You allow existing customers to buy existing models and use them. Voila. End Times, Compendium style army books. Unbound. Mercs / Allies, etc.
How do you reduce cost of updating the massive encyclopedia of books that represents fantasy and 'turn' ? Print fewer books, make them larger so you go to print less times.
I really think they are trying some radical things with Fantasy (or gearing up to do so), and i hope that they don't get cold feet and puss out on it. The game is about a quarter of their earnings right now. It's difficult to see how a new army (say, chaos dwarves, just as a for instance) could ever come into the game right now as bloated and unwieldly as it is... so i think they have to trim the fat, suck in the gut, fit into that corset, with the game before they can start expanding. Condensing individual flavors of armies into overaching themes of armies could make this work.
If you're still reading this, thanks, it got long winded. Even for me.