Chances of this fight happening: 0%. He will either retire now or lose again against Kovalev and retire.
I'm thinking the longer the idiot takes contemplating the rematch... the more he'll hear the truth about who really deserved the nod and also hear the predictions on a rematch. And that will no doubt lower the chances of Ward wanting to step in with Sergey again. I don't think the rematch is happening. Plus Ward seeing the way his buddy Hopkins went out doesn't help the odds of a rematch either.