Throwing out my random timeline after thinking about it:
-console announcement around TGS (Sep 2011)
-interface/case reveal at GDC (Feb 2012), maybe a game reveal or two to show off it's features
-games blowout at E3 (Jun 2012), 3DS-like focus on 3rd party support
-JP launch first (Sep 2012)
-NA/EU launch soon after (Nov 2012)
...in terms of 1st party development, I think EAD Tokyo is going to have a launch game for it, maybe the next 3D Mario even, or maybe a Wave Race revival or something (Koizumi does love his water physics). For 3rd parties, well... I hope you like ports.
I think this E3 is going to be almost all 3DS though. Nintendo's going to have an insane lineup for the thing, and they'll want to try and spoil NGP's rollout.