Demonic instability is in the new book. What that really entails is not quite clear, but I'm guessing it will be 2D6 plus wounds not saved, minus leadership. Also noted there will be a leadership reduction army wide ( plague bearers are now Leadership 7 from a 10 in the last codex). So your 5 man plague bearer squad take 2 wounds after a round of combat from a 10 man assault squad punishing them. Rolling a 2D6 nets a 8, add 2 for the wounds taken and subtract 7 (8+2=10-7=3) so the squad take 3 more wounds that are not possible to save against. So you basically lose the squad. Now as FNP isn't a save and can be taken by things like perils I'm not sure if they would get a FNP for the 3 wounds.
So no we know that this will be a rule I think we'll see the addition of banners that provide a similar effect to stubborn. Likewise my guess that greater daemons with 6" will provide such a save as well as heralds and IC's that can join a squad will instill such a bonus. So if you don't run a banner or an IC in the squad I think you will have to run a large squad so as not to be banished to the warp. example is 15 plague bearers take 2 wounds, roll a 8 so your back to 10-7=3. 5 die but you don't lose the entire squad. MSU for deamons might be really bad now. Guessing we'll see now a point decrease for sure with option to buy banner for 25-35 points giving stubborn etc to the squad.
I'm pretty sure we lose fearless and will just sub Daemonic Instability (DI) for this. I also think Eternal warrior is out for most of the lesser daemons at least.
Deepstrike deployment seems to be not a requirement anymore. Units can if they have it in their profile, but most will walk on. (Making the regular troops much worse if there are no transports etc )
The CSM dex has the daemon prince marks. Pay attention as these will be what the various gods provide to the units. Nurgle will have shrouding for all, Khorne Rage, Tzeetch re-rolls on 1's for saves. etc.
I'm pretty excited about this dex now. I think daemons will be a totally different army from what they were and more inline with the other 40k armies in terms of deployment etc.