Well while we wait for everyone to finish writing their opinions/defenses/eulogies for John Carter and the people behind the film (some of which I think is a little premature) it looks like the Edgar Rice Burroughs estate has some other plans for the future. While snooping around I came across two new books-all estate approved-that are in the works. The first out will be Jane: The Woman Who Loved Tarzan by historical romance writer Robin Maxwell and is currently listed on Amazon for a September 2012 release date. Maxwell talked a little bit about the book and her comments can be read at http://www.tarzan.com/meets/ (just scroll down a little to find them).
The other book I have little information about: I noticed on the Wikipedia page for the Venus series a sentence that the Burroughs estate had hired a writer named Neal Romanek to pen a new adveture of Carson and company called Skies of Venus. What little I could find was Romanek's Twitter page which indeed does mention that he is working on the novel. Currently there is no release date set so I'll keep an eye out for any future news. You can read more at Romanek's page at http://twitter.com/#!/rabbitandcrow.
Artwork above by Joe Jusko-just want to give credit since I liked both pieces.