I think the key fact, obviously, here is that Ukraine for better or worse isn't a NATO member. (Duh, I know). If Putin decided to use his Putin Doctrine (hey, did I just invent a term?) to justify sending the Russian army to protect Russian minorities in say, the Baltic states, that's when the proverbial inks hits the fan. (turn and burn baby) I highly doubt that he would, but the man has surprised me before.
It would be nice to have Ukraine in the NATO and EU sphere, but at the same time, it would also probably be a huge chore for both bodies to get a tumultuous Ukrainian government to follow through on any sort of resolutions.