It really depends on how the rest of the war develops. The Polish-Soviet War had very dramatic shifts back and forth. A lot depends on chance. However, the Polish Army was experiencing problems by that time. They were simply being stretched too far.
Assuming Poland wins, some kind of Ukrainian and Belarussian states will be established. Poland will likely grab a lot of land that Ukrainian and Belarussian nationalists would like for themselves (wherever there were Poles more or less), but they'll have their own states. Pilsudski would likely want a multi-ethnic state (Intermarum/Międzymorze) that could balance the power of Germany and the Soviet Union, but it is unlikely to happen. Too much nationalism at that time. In terms of borders, it mainly depends on how successful the Polish armies were.