Pixar is working on the script.

Andrew Stanton says that some things will have to be changed in the adaptation. Given that Dejah Thoris is mostly nude in the novels, I would imagine that that would be one of them.

Stanton also says it'll combine live action and animation.

After languishing in development hell for several years, it's now scheduled for March 2012.

I've been reading about the various aborted versions of how to adapt these novels into movies for years and I think that everybody may be putting too much effort into something that won't be worth it in the long run.

Don't get me wrong, the stories sound interesting enough but some 100 years after they were written and we have actual remote operated craft on Mars exploring the planet the idea of a civil war soldier being transported there and finding a post-apocalyptic civilization living on the planet sounds absurd. Granted other media franchises have been able to play alternate history; but it's rare.

In the 90s the Hercules and Xena shows managed to do it. The Pirates of the Caribbean movies did it but they were so far in the past that nothing of what they did really affected today. In the case of John Carter you're talking about a movie who's central premise violates both our own history and everything that we know about the red planet. The only modern media franchise I can think of that does the native Martian civilization thing is Futuramma and it's played for laughs. Perhaps the books have a big enough fanbase, but personally my first exposure to the franchise was reading updates about the movie's development on websites.