It's on Nintendo's 2003 release list. There's only been one video that I know of and it doesn't show any gameplay. I would expect that we'll see lots more at E3. I want this game so badly. Mario Kart defined my freshmen year in college.
Miyamoto did say in a interview that if he did show screen shots it would give something away about the game. Online play perhaps? I wish I could remember where I read this but it was from a reputable website and a direct quote.
Just freshman year? Seems like it dominated my entire college life. Apparently it was a kick for my roommate and his friends to play this high. Listening to Bob Marley. At 3am.
Dang I'd like to know if this title is going to be out soon. There's a deal on a Gamecube and my girlfriend loves Mario Party, but I don't want to buy the system for just one game (and I already own an XBox and most games I play are cross platform and I already own for that system).
Nintendo's already announced several titles to be released as late as August, with no Mario Kart news in sight. I would guess that we might see something at E3--for maybe a possible Thanksgiving-timeframe title. I don't believe that Nintendo has any other huge games (Mario, Zelda, Metroid) in the works for their "big" Christmas game this year, so maybe Mario Kart might fit that bill.
Nintendo's big titles for the holiday season are the alleged "World Smash" titles, which are supposedly online enabled, Mario Kart/Tennis/Golf being the most likely suspects