I’m curious as to how that would shake out; due to the mass migrations as the borders were being re-drawn after WWII, Poland may have little reason to take back land. The Russia/Ukraine border was set in the 1990s, and very imperfectly (Stalin transferred Crimea to Ukraine never expecting they’d be an independent country, and many ethnic Russians were left on the Ukrainian side of the border).
The problem of unwanted ethnics is easily solved by ethnic cleansing. Nobody is going to say a thing once the ‘good guys’ are doing it.