Considering that the P800 comes with a movie tie-in game MIB II first person shoot 'em up, I'd guess it will be released on, or about the same time as the movie. MIB II is scheduled to hit my local (UK)Odeon cinema on 2 August.
P800 out end July / early August, probably
Expansys says 30 days...
http//www.expansys.com/product.asp?code=P800