I don't think any major partition of Ukraine is likely in the nearest 30 years.
I thought in this direction. But its kind of maximal delay.
In western Ukraine time will work for Poland. In rest, time will work for Russia. Outside of Ukraine situation will also change. Serbia will be stronger and it means Slavic South safe from outside non-Slavic hostile presents, with interests of Poland and Russia in perfect balance, here in the region. EU won`t exist and Visegrad would emerge as unique power. Germany and France would be probably already devastated by internal racial and religious Civil Wars.
See, in that situation, Poland and Russia just shake hands. Ukraine would dissolve naturally and peacefully.
Baltics? Well, with weak Germany, like Ukraine, it would turn to stronger, to Poland and Russia.
When that is over, well, Russia turns to closer ties with Iran (read old Persia) and strengthen further Eurasian Union. At the same time Visegrad around Poland and ``Little Schengen`` (ongoing working title) around Serbia becoming closer and finally merge into Central European Union.
Belarus? It depend.