Unless there is a beatdown on one of the fighters, they would be crazy not to do it all again. Its worth too much money.
Chris Maddox of SI recently asked Arum about the possibilities of a rematch and he quoted Arum in saying something to the effect of: "Would a freed prisoner ask to go back to prison?" Arum's basically likening the idea of collaborating with all the various entities who are involved with this fight for a second time to going back to prison.
I've thought a rematch was almost certain to occur (unless as you say one suffers a serious beatdown)... Theres simply too much money to be made.