JMS announced at his panel at San Diego Comic-Con Friday July 22, that he's decided that going forward he's out of the comics business (barring a few things already in process) in order to concentrate on writing novels and plays in addition to TV and Film.

Other announcements:
- JMS had cataracts and Fuchs Corneal Dystrophy for several years but after successful surgery, now has better vision than ever
- There's an upcoming project involving three names: Bradbury, Gaiman and JMS.
- Midnight Nation will be becoming a TV series.
- Rising Stars has been optioned for a feature film.
- Re: The B5 movie, JMS is working on building his 'street cred' in order to be able to approach investors for over a hundred million dollars. He thinks after another TV show or two and a couple more feature films, he should have achieved that credibility for Studio JMS.

For the longer report, check out the post on the JMSnews forums:
http://jmsnews.com/forums/showpost.php?p=133478&postcount=46
Video at: https://www.youtube.com/watch?v=VN_RJcV64ME (sorry for the shakiness)

ETA: JMS wrote about his leaving comics:
http://www.newsarama.com/30468-why-j-michael-straczynski-is-leaving-comic-books-in-his-own-words.html