It certainly feels odd that a Mario Kart update is coming so soon. Or maybe it's Double Dash!!'s late release in the GCN's life that's getting to me. IIRC, Mario Kart 64 was released quite early in the N64's life.
Anyway, while Mario Kart Wii looks a bit too slap-dash made, it's nice to see that the developer is adding something a bit new with the motor bikes. However, it's a shame that the tandem rides have been left aside. It would've been neat to have karts, tandem karts, and motor bikes in one game. Still, thirty-two tracks with sixteen new for the Wii installment and a battle mode with more people and bigger arenas should make this game an adequete addition to the series.