It'll be George for sure!
The fact that they're bringing in a Serra member as replacement means either Matt or George left! or it'd mean Serra gets 3-1 in the semis and Hughes would proly "throw a fit"
Also if Matt left I don't see them bringing in John to face Mac again in the semis!
Reason why is wont be Mac: He hated the house a lot, and was only there to win and not be on TV.. so why would he spend the whole 6 weeks in the house just to quit at the end when he's 1 fight away from the final!
It could be tommy tho but I'd put money on it being GeorgeČ