You're not the first to suggest that. Rumor hath it, that at least one of the others was FURIOUS at Maines. Perhaps it'll happen. Their music is great, and I'll bet that dumping Maines would only improve it.
It would have been more effective and convincing if they'd dumped Maines right away, and made a public pro-Bush, pro-troops statement in the press conference. But perhaps they'll do that at the end of this tour? We'll see.
Dumping Maines couldn't hurt the "look" of the group either.