These feel a little dubious but lets get to it.
Rumors via Simply Warhammer- Not certain who translated them to text
1. Rogal Dorn Tank is confirmed, it has less than 18 wounds and is Toughness 9.
2. Hopefully Baneblades and variants are also Toughness 9, but he didn't hear anything about them, so fingers crossed.
3. Tank Commanders are nerfed to BS 4+. Ouch. Turret weapons no longer fire twice, but they have a +1 to hit and they can now shoot out of combat (as in, if you're locked in combat with a melee unit, you can still shoot your turret weapon at another unit not within engagement range with your tank, hence allowing you to still shoot blast weapons even though you're locked in combat). Sponson and hull weapons remain the same, so they are probably still BS 4+ and have to shoot into combat with a -1 penalty.
4. Probably get a bunch of tokens (like Genestealer Cultists? Crossfire markers and whatever).
5. Deathstrike now can take 3 missiles, seems like its weapon has improved, and firing mechanism has also been changed. Main explosion does lots of damage to the primary target, then 3D3 mortal wounds to units within 6" of the primary target.
6. Death Korps of Krieg are in the book as their own new regiment, will have a new Regimental Doctrine, Stratagems, Relics, Warlord Traits and stuff.
7. Rough Riders are back in the codex, no longer shunted to Legends and having a new model.