The crimea is gone. Russia will not give it back, the West is not starting WW3 to save territory for the Ukraine. When the Russians did this in Georgia no one flinched. Rusians noted this and have used the same strategy. The Baltic States must be Shitting themselves.
In the long term whilst fracking could kill the world, it does produce shitloads of gas and oil. Russia, meaning Puttin, is very aware that it is his time to strike now or never. Putin knows he has nothing to fear. He is the closest thing to Stalin since Stalin. No one can survive a political attack on him. He knows that and so do most Russians,
Will The Ukraine be attacked, not unless they attack the Crimea. which they will not. Russia sells gas because it needs hard cash. It is still a backwater, when it comes to industrial production and Putin knows that if it switches off the Gas supplies it will also destroy its ability to develop as an economic power. My opinion is that after much sabre rattling the new borders will become accepted and the status quo will continue.
I think Putin knows that any more expansion will lead to crippling sanctions, not short term but long term. Europe buys its gas from Russia because it is easy and cheap. There is lots of gas world wide. Europe is just know starting to realize how much is under their own feet. (fracking) Russsia in the middle and long term must keep its customers happy or else all the gas it has is not going to make it any money. It's customers will look to securing supplies from other means if it looks like it can be used a s a weapon against their survival.