Well, expect at least one Flyer. A single Flakk Missile isn't going to do much against that.
Those are Grey
Hunters by the way. Grey Knights are something else entirely!

Also, your
SW friend is possibly crazy for dumping that many points in to Wolf Guard at this point level, but especially crazy for their load out. I say this as a Space Wolf player, who does almost nothing but Drop Pod these days even.
Honestly, I'm not sure why he's bringing the Wolf Priest either. The Wolf Guard are basically just going to be the same as his Grey Hunters, but non-scoring, more expensive, and have 9 one-shot Meltaguns duct taped to their Boltguns. They can't shoot on the charge unless they use that Meltagun shot. They aren't particuarlly scary in close combat, so don't need the re-rolls from the Wolf Priest. They don't have bad leadership, so they don't really need Fearless. And he's not taking Saga of the Hunter for the Stealth and option to Outflank? It i worth it even just for the Stealth.
Against other Space Marines he probably isn't going to fare well. He doesn't have anything to really deal with them in the Assault Phase, and he only has the one Character.
He should really consider taking out some Wolf Guard to beef up his Grey Hunters, and possibly replacing that Wolf Priest with a Rune Priest. Something like this maybe:
HQ
120 points - Rune Priest (Runic Armor; Living Lightning, Murderous Hurricane)
ELITE
205 points - Wolf Guard (5; 2 Combi-Plasma & Wolf Claw, 2 Combi-Melta, 1 TDA & Assault Cannon & Power Axe, 1 Drop Pod)
Troops
205 points - Grey Hunters (9; 1 Plasma Guns, 1 Wolf Standard, 1 Mark of the Wulfen, 1 Drop Pod)
205 points - Grey Hunters (9; 1 Plasma Guns, 1 Wolf Standard, 1 Mark of the Wulfen, 1 Drop Pod)
It is a little more flexible in that we can give the Grey Hunters a Melta shot or the Rune Priest if we need to, or leave the Wolf Guard all together. It just depends on what we need to do. The Grey Hunters, particularly with the Combi-Plasma/Wolf Claw Wolf guard, are more capable in close combat. This will become important since we're dropping in the enemy's lap.
Honestly though, Wolf Guard are expensive at this point level. I'd rather take more Grey Hunters if it were me. Replacing the Wolf Guard with another 10 man Grey Hunter pack on foot for a Wolf Priest with Saga of the Hunter to lead, while giving all 3 Grey Hunter units Wolf Standards and Mark of the Wulfen, is much more appealing to me. You start out with only one Grey Hunter pack on the table but with the 2nd and 3rd coming in on Drop Pod and Outflank it can be fun.
Any reason for the Deathwing Knights over regular Deathwing by the way? I'm not 100% familiar with the Dark Angel Codex yet. I get why you'd take the Ravenwing Knights, but wasn't sure what point over normal Deathwing the Knights were really offering you.