Just saw today's episode and yep, Alain does seem to be siding with Team Flare, so it looks like I'll also be wrong about there being a rematch. Perhaps they'll even take the League trophy back from Alain, or he'll feel remorseful and undeserving and give it up on his own. That wouldn't be a completely legit way for Ash to finally get a league victory, but beggars can't be choosers!