Well, I've seen the following blurb on them:
SPECIAL NOTE: This limited edition All-in-One Army Box is a special introductory offer aimed at new players as well as existing players wanting to add a new faction to their collection. It is available through distribution in very limited quantities. This All-in-One Army Box is over a $200 value with an MSRP of $129.99, representing a 42% savings off MSRP. All orders will be fulfilled on a first-come, first-served basis, even if submitted before the new release due date.
The Khador set just came out, and it looks like the rest will trickle out over the next few months.
Here is the release schedule:
Khador......out
Skorne...... Feb 25th
Protectorate.. Mar 18th
Legion......Mar 18th
Cygnar.... Apr 22nd
Trollbloods...Apr 22nd
Cryx........ May
I'd presume that there will be an army box for Retribution and Circle at some point in the future. I'm gonna
my butt off if the Circle set comes with two sets of Shifting Stones.
Like a lot of stuff
PP comes out with, if you don't get it right away and it goes "out of stock", you might be waiting a LOOOOONG time for it to get back in stock.