I think Conan should make a very public spectacle of returning to his old writing duties for "The Simpsons". It would give that show a much-needed boost in both the actual writing since Conan wrote many of its best episodes, and publicity for a new talk show he could host on Fox, a win-win for all parties involved. Leno's audience is aging, and to be blunt, most of his 'supporters' don't stay up late enough to watch his show anyway. Those who complained the most about Conan's humor being too "edgy" didn't watch "The Tonight Show," Leno or Conan.
I've never understood Letterman's appeal in any fashion (through Craig Ferguson is downright hilarious on a regular basis.) That sets the stage for Conan to take a Fox late show to #1 and NBC and CBS to return to fighting Leno against Letterman; both are dying horses, but Leno lacks the 'hipster cred' factor that seems to keep Letterman afloat, and NBC may be justly rewarded for its actions now.