I don't know if anyone else has heard this yet. It hasn't been OFFICIALLY announced, but one of FUNi's representatives, Lance Heiskell, said this just recently in a FUNi talkback thread concerning the OP/ED themes for the Adult Swim run of the series.
We're going to change up the opening halfway around the second season on [adult swim]. Don't want to say what opening just yet.
I'm thinking that's a good sign that it'll be Rewrite, eh? =)