Seems like this could be the surprise for the E3.
Additionally, an accelerometer is said to be incorporated into the handheld. If you’ve toyed around with pretty much any smart phone, you’re familiar with the screen tilting action. We imagine this will lead to many balance beam and pinball minigames.
These game creators said the games for the new handheld will be completed by the end of the year. Whether Nintendo releases the unit by then is still mysterious. However, enigmatic sources say that we might see an E3 2010 announcement and a release later this year.
http://gameinformer.com/b/news/archive/2010/03/12/nintendo-ds-successor-already-being-developed-for.aspx