Apparently he's coming out with another book. Here's some info about it from the Wikipedia article:

Ender in Exile is a yet-to-be-published science fiction novel by Orson Scott Card, which will be a prequel to Speaker for the Dead.

Very little about the book is known at this time; Card announced it, along with Shadows in Flight, all that has been published on this book is it will take place about 2600 years before Speaker for the Dead and about 400 years after Ender's Game. It is not known where this book is in relation to "Investment Counselor". However, it is likely that it would be after the story Investment Counselor, due to the relative age of Ender in the rest of the series. It is also known that the planet Ender visits was founded by Achilles de Flandres II, also known as Randall Firth, the son of Bean and Petra. He was one of their nine embryos which was implanted into a woman named Randi, who believes the child to be Achilles'. Although not confirmed, it appears that Achilles de Flandres II has Anton's Key turned. There has also been speculation that the title of Ganges might have some thing to do with Virlomi. Also noteworthy: in Xenocide, Valentine and Miro refer to experiments performed by Gangean Hindus with regards to the nature of philotes.

At this time, the expected release date is November 11, 2008.