Greetings there. There is no specific as of yet other then 2010. During the trailer you see 3/25 in the missile count speculating that the release date will be 3/25/10 (March 25th, 2010) but this is just speculation as nintendo has said nothing of a definite date as of yet.
also check the metroid wikia This is from another person: June 27 2010!
Edit by Phazon lord on 5/4/2010. The release date was original 6/27/10 but has been pushed back to august. You can see a timer on the Wikitroid site.