Anyway, ultimately this will be decided by Gavin and so far he's been saying he wants to raise the block size limit.
I'd say ultimately it's the main services (MtGox, Bitpay, BitInstant, BitcoinStore, WalletBit, Silk Road etc) that will decide. If they all stay at the same side of the fork, that will likely be the side that "wins", regardless of Gavin or even miners' will (most miners would just follow the money).
Of course that services have a strong interest in staying on the branch that's more professionally supported by developers, so yeah, if most of the core team goes to one side, we could predict most of these services would too.