This ship has long sailed. If the Ukrainians obeyed the Minsk agreements, Donbas and Lugansk could have been still theirs. Until the collapse of the Istanbul talks they had the chance to keep the rest. Now they’re quite out of options.
Even if Russia manages to hold on to Donbas and Lugansk, which is not a foregone conclusion by a long shot, it will be a pyrrhic victory that they will regret for a long, long time.