It's a highly unlikely scenario that Russia would want to expand the war pat Ukraine, and everybody with a functioning brain understands that. What will happen is that Russia will take over all the territory in Ukraine that's either pro Russian or neutral.

The rest will be left as a problem for the west to deal with. It's going to be a dysfunctional rump state that's not economically self sufficient, and where there will be massive resentment towards the west over the betrayal. If Europe allows it to fall then they will be faced with a new refugee crisis, and if they don't then it's an economic black hole that they have to keep pouring money into. Either scenario will only make the already desperate economic situation in Europe even worse than it is now.

It's going to be easy for Russia to make deals with individual countries as public unrest in Europe continues to grow. Hungary and Slovakia have already flipped to Russia, it's likely only a matter of time before Romania, Czech Republic, Germany, and France do as well. At that point we're looking at the end of EU, and possibly the end of NATO as well. Especially given that the US will almost certainly be pulling back under Trump.