It's obvious the terms of the bet are ambiguous (Core vs XT will both claim to be the "real" Bitcoin)...
It's not ambiguous at all. I win the bet if, by this time next year, a block larger than 1 MB exists on the
longest proof-of-work chain whether that's XT, Core or something else. You win the bet otherwise.
Care to make a wager, iCEBREAKER? 1 BTC that the longest proof-of-work chain contains a block larger than 1 MB by this time next year (10-Jul-2016). Escrowed by someone in this thread (2-of-3 multisig), of course.