We likely haven't seen Nintendo's response to Microsoft's and Sony's foray into motion control yet: Motion+ was a preemptive stab, assuming the other two were going to announce something at E3 2008, and Vitality was announced at the same time as Arc and Natal. Vitality + Zelda with Motion+ could be the extent of that response, but I doubt it.
Before E3 last year, we didn't know about NSMBWii, and we all know how that turned out.
I would think that there is at minimum one major unannounced Holiday 2010 game coming from Nintendo, and likely a couple teasers for 1st half 2011 games (my guess on the teasers is whatever Retro is working on, Pikmin 3, possibly for DS, and either Starfox or Pilotwings).
I think Natal will be a big part of Microsoft's E3, and along with Reach will be their main holiday focus. Probably one other big core game, but it will likely be a teaser, and a year away.
I think Arc is dead in the water. Microsoft did what Sony didn't expect, and actually attempted something truly innovative, rather than, 'me too'.
As an aside, Microsoft as a corporation has been impressing the shit out of me recently. I've owned a Mac since the mid 90's, and never owned a single Windows machine, but hey, give credit where it's due, their tech guys have been swinging for the fences in the past couple of years. Zune HD, Windows 7, 360, Courier, and Pivot are all great pieces of tech.