I guess looking at the map it's conceivable that a West and East Ukraine could form, with the river being the wall/boarder.

But as the European response has been so weak (based on their dependence on Russia for energy), he'll just press on and take the lot while the military hardware is there, declare it yet another new nation, and shift his missiles and nuclear weapons there and claim that because it's a new state, all prior agreements are void.

We've all seen this behaviour on the playground as kids, it doesn't stop until someone big or brave enough takes a big stand and does something heroic.

The last two years has also taught him that the gen pop is very compliant and won't protest much, so it's all a fairly low risk while the rest of the world is consumed by covid.