After the amount of effort Russia has expended getting that much kit and manpower into place, hugely increased maintenance / prep requirements for equipment, training requirements, food/water, fuel expenditure plus all the stuff you'd never see on the news (human intelligence, air and naval asssets, space, planning, internal politics ect.).
There's no way they'll be willing to walk away with nothing. Russia's population appears to largely support their govs position - and the guys at the very top aren't going to suffer that badly if there are economic sanctions, no matter how severe.
I think they'll get eastern Ukraine at a minimum - they have an overwhelming military advantage over the Ukrainian forces, and the cost of stopping them will be to high for the West to want to take on.
Depends how much of that military movement is real - there is no doubt they've built up a lot of equipment and started to move a lot of man power - but from my casual digging on some of the videos cropping up on Twitter a lot of what purports to be units moving to the front are forces which have been moved in months ago and for some reason - possibly readiness drills or other exercises - moved away from Ukraine then back again to their bases to make it look like far more is moving than actually is - though the build up is still substantial.
Given all that has been going on though I do find it suspect that Russia will want to walk away from this without getting something significant out of it, which so far they don't seem to be. The lengths which have been gone to are high and quite expensive for Russia including sending lots of ships the long way around to the Black Sea.