I can't see him putting up Britney now, he's made sure he's safe with her and Ragan, and he has his suspicions about Enzo and Hayden, so he'd keep Britney around because if she wins HoH she is putting up Brendon and Enzo. Plus, I think if he put Britney up this way, he'd lose her Jury vote.
He'll go for the safe option, which is Kathy. He has his reasons, she was the one that knew about the pretzel message that Rachel left, and did nothing to stop Brendon reading it. She is also suspected of being the saboteur. And it gets rid of a a weak player that some other housemates may have intended to drag to the end as a goat. Plus, he won't make many people angry with that choice.