According to Amazon.com "Song of Susannah" (the Dark Tower Book 6) is being released on June 8th. The Editorial review is very intriguing, but I won't repeat what they say here for those of you who want to be surprised. I WILL say there are some rather strange plot twists... I can't wait!
And for those of you who procrastinate, the review says the seventh and last book, Dark Tower VII: The Dark Tower will be out in a few short months.