[quote name='io']I figured Mario Kart would be their big Holiday 2008 release, especially given how Galaxy and SSBB are coming this year (as promised). Wouldn't have surprised me if they waited till 2009 for it, actually...[/QUOTE]
Well, let's not get ahead of ourselves here.

2009 may be a fantastic number given Nintendo's history with anticipated release dates (that includes MKDD, a Zelda or two, Metroid, Mario, etc.).
It's still hard to believe that they'll want to put the newest MK on shelves with SSBB, SMG, and MP3 all sitting there with ~6 months of dust on the oldest of the three. Plus, they may want to see how the Wii online experience goes over with Strikers, though I doubt there's any kind of analogue between the Strikers and MK online to make the experience useful. However, Nintendo's working
somewhat differently than others this generation: maybe this idea of "momentum"--that is, quickly building sales and a game library around a cheap console over two holidays--doesn't preclude having 4 or 5 huge titles on the shelves within a 6-8 month span (though 3rd parties can't be too happy about it).
Also, Q1 '08 is very possible given 1) the rumors that the game was nearly complete and built largely upon Arcade GP and 2) the released screens, which confirmed the Arcade GP pedigree--somewhat--as they looked very similar to screens from Arcade GP.
I'm eager for more official screens and videos ASAP. I'm sick of rumors about this title.