Unfortunately, I don't think that Conan has that many options available to him, if he wants to remain on a broadcast network. ABC isn't going to displace both Nightline and Jimmy Kimmel Live from their respective timeslots. FOX might want him, but he probably won't get enough clearances from local FOX affiliates.
I think Conan would be wise to shop himself to cable networks. In fact, Bill Simmons had a great idea when he proposed that Conan take the 12:00 slot on Comedy Central, following The Daily Show and The Colbert Report. Plus, cable would give Conan more artistic freedom than he would get on a broadcast network.