We'll start with Allies. This will bump Daemons, and every army except poor, poor Tyranids. There's several things Daemons would want from Chaos Marines- melta, Heavy weapons in general, and transports. (Note that bloodcrushers are infantry. This means you can put 8 in a rhino they steal from another unit)
Good options look like Havocs, Sorcerers for psychic powers that Daemons lack and may need, depending on how 6th psychic powers pan out, and... anything that strikes your fancy.
Depending on how the allies chart pans out, it looks like they can get stuff from Tau. Broadsides, yay!
Power Weapon changes only hurt Daemons. AP3 power weapons means you'll have to find another way to deal with terminators than killing them with Bloodcrushers. :( And the 5++ they give is already standard on Daemons.
I hate AP3 power weapons. As if Marines needed another advantage over every other army.
Anyways. Moving on. There's quite a few rules that generally nerf vehicles, and that's very helpful. In short, be more careful with and/or don't bring soul grinders.
BS1 Reaction fire makes Flamers absolutely deadly. They can jump in, Flame, then when they get charged, Flame again. Nothing will live. ! Actually, Flamers may entirely replace Bloodcrushers, seeing as they just "ignore armor," so they can melt Terminators!
Bloodcrushers were always expensive anyways. Though I'll be sad to see them go.
5+ FNP makes Nurgle cry... unless you bring Epidemius! Then you'll still be saving on 3's once you kill enough models! Fun!
Jump Infantry getting one attack at I10 on the charge... not actually that helpful to Daemons. Furies still don't have power weapons, Winged DP's are still insanely expensive, Bloodthirsters still shouldn't be fighting infantry, and Keepers of secrets don't fly, and just have all their attacks at I10.
Overall, I think Daemons will be unintentionally helped by 6th, mostly via the general vehicle nerfs, but also flamers being death machines.
at least, if the rumors are all true. Which is doubtful. But the recent ones seem to hold water.