Up next for 40k sounds like may timeframe for a chaos codex. Rumored to expand upon 4 major legions.
New plastic raptors
New plastic plague bearers
New character sculpts, not sure if abaddon is included...
I think most if not all of this has been mentioned before.
On top of this, I'm hearing there will be a few blister releases for other armies between now and summer. Even with WFB likely to take the spotlight in April, I'm being told to expect 2-3 blisters for 40k.
Likely candidates include missing characters for Nids, Necrons, DE. All of which have sculpts ready.
But that's not all that's in the book from what I hear. And the conflict in what I've heard is that they expanded upon the 4 chaos gods, or they expanded upon the 4 legions devoted to those specific gods, so I'm not certain which is true right now, if either.
I have heard from many sources traitor guard and others are in the book, but nothing close enough for me to have a lot of faith yet there.