Harry Potter and the Deathly Hollows Part:1 - will be released in 2010
Harry Potter and the Deathly Hollows Part:2 - will be released in 2011
The other books were adapted to movies mainly by deleting certain characters and subplots that served as background and were not critical to the plot. The makers felt that this was impossible for "The Deadly Hallows", as most of the subplots and (seemingly) trivial characters are eventually tied to the conclusion. Also, to give each character's story and the series as a whole a proper closure, the producer's felt that they should not even try to cram all that information into a single film, and the decision of a two-parter la Kill Bill was made.
Not only this but there are rumors going around that the final movie meaning both movies will be R rated or in UK 15 rated, this is because of the dark nature of the book as well as the high body count.