According to the Japanese magazine, Nintendo Dream, the Gamecube Mario Kart will feature online gaming, definintely. Nintendo however are yet to confirm this so it is merly a rumour.

New Sega Game
United Game Artists, a division of Sega and famous for games such as Rez and the Space Channel 5 games, are working on a new Gamecube game. The game will not be another Space Channel 5 game and will be unveiled in Spring.