Release date is March 27 in Japan.  And a quick reminder for those people who have never imported before, it costs more.  A lot more if you get it right away, and a little more if you wait.  GBA SP was $150 at launch (expected $175), and my Gamecube cost me $380 (after deducting price of games and mem card that came with the bundle).  If there is a huge demand for imports, we'll pay for it.
NCSX expects to be taking pre-orders next week.