So long as World War III doesn’t occur by miscalculation, then rump Ukraine would remain formally under its representatives’ political control regardless of whoever they may be by then, while the western part that used to be part of Poland would fall under its “sphere of economic influence”. Formal reincorporation is unlikely though for socio-economic reasons, let alone the lack of public support, though a confederation of some kind could eventually take shape at a later time.
This scenario sounds rather likely. The US Empire would like to keep a rump state from which it can launch terrorist attacks against Russia.
Well, Russia will call them terrorist attacks. The New York Times will call them freedom fighters striking back against the Evil Empire.