I'm going to lay out the most likely "ending", I think, which isn't an end at all.
At some point, both sides agree to a cease fire (which mostly holds).
Then the talk talk talk about withdrawals.
After much talk, Russia agrees to some modest withdrawals, but stays in Donbass, Crimea of course, and around Mariupol.
Then there is more talk, and some minor eruptions of fighting here and there by separatists.
Then they agree to talk some more, with some third party, maybe the Young Turks.
Then Russia threatens to abandon talks, but they talk some more.
Europe decides all this talking is leading nowhere fast, which is true, and decides they need hydrocarbons from Russia.
Five years from now, nothing is really resolved, sanctions have weakened considerably, and life goes on.