For now, we know it's being described as a "visceral hardcore RPG with innovative new combat mechanics". Which, admittedly, is not a lot to go on.
Deck13 teamed up with CI Games for Lords of the Fallen, but thesequel will be handled entirely by CI. There's been no official explanation for the split, but it's not hugely surprising that two distinct development teams would want to go their own way.
The only image released so far, which you can see above, seems to show a soldier with a cybernetic implant wielding some kind of chainsaw weapon in one hand, and a power gauntlet in the other. From this, I have deduced that at least part of the game will involve hitting people with futuristic chainsaws. You can quote me on that.