While we don't know the intimate details of his contract it appears that he is barred from hosting a show, so guest appearances may be permitted.
I too thought it would be great to see Coco on another show as a guest. Letterman would be near perfect for that. I know I'd tune in for that one.
And yes, I'm not going to be watching Leno when he comes back. I didn't care much for him before finding him to boring most of the time. Leno is too "safe." Conan was a bit more risky, but ultimately more entertaining, IMO.
When Conan does come back, I really hope he can find a way to bring back certain characters from the show, albeit in a different format.
Masterbating Bear? How about a giant masterbating chicken instead?
Triumph the Insult Comic Dog? How about Conquest the cagey cat, or Manny the pissed-off Poodle?
I just think it sucks that some of these characters in essence have been written off. While individually they may not have been the greatest, collectively they made up a fantastic ensemble funny tidbits.