My daughter said he'll fire all four. I said "no way" NBC would lose 3 weeks of programming. DOH! So much for logic. But for a show that I expect little drama from, it was a shocking and pleasant surprise.
They've had it in the can for a while, so they probably have scheduled around the number of episodes already. I can only assume that Donald gets paid by the season, not per episode.
There's also the possibility of a "loser's bracket" show where they go 2 vs. 2 for the right to get back on the show.