Maybe it is becouse I am new to grey knights but does this mean that a deamon that has a 4+ sv that is considered invulnerable will not get any sv vs an incinerator or psycannon?

AGREE!

no saves for demons!

our weapons were made to destroy demons!

(I hope I'm right)

Don't forget psycannon bolt upgrades on our bolt-weapons as well. Hopefully these IS-negating weapons will make up for the lack of firepower due to our low model count.

Yes.

Imagine a squad of eldar warlocks in cover.

And suddently a big template of holy incinerator fire covers them!

No invurnerable saves, no armour saves(ap 4), no cover saves.

NO SAVES!!!! MUHAHAHHAAA!!!

Hope the new deamons don't get armour saves.

Tell your opo to keep them dice in the pocket for them save

No Lesser daemon or elites or fast have armor saves, only juggernauts have 4+ (and you psycannons are ap4 )

Problems:
Greater daemon of khorne
Herald of Khorne
All Daemon Princes

They all can have marine saves

MOST DANGER!!!
Tune you army with LOADS of Psycannons, forgetting to get some Dreads with Twin Las... why?... because they have their own dread but with 1 more point of frontal/lateral/AND BACK! So psycannons won't do anything to him.