Joe Straczynski, in the panel we attended at the SDCC, mentioned that he’s signed an exclusive agreement with Marvel. Whether that bodes ill for future stand-alone efforts like Rising Stars or Midnight Nation I’ve no idea. He did indicate that he (and Romita) are on Spider-Man until Marvel gets tired of them.
In response to questions, he mentioned other characters he’d like to work with would be Dr. Strange, Captain America (playing up the “man out of time” aspects) and Iron Man. He thinks he has hooks to the characters which have never been explored, assumptions that could be called into question (akin to “Aunt May is frail and can never find out about Peter,” or “Peter got his power from radioactive spider venom,” or “Peter is and must remain a freelance photographer”).
I am so there with any of those titles.