Mario Kart 8 will be the worst-selling Mario Kart ever. UPDATE: Nope, my prediction was wrong.

[cuberandgamer]

Zekkyou said:

Miyamotoo said:
No, better than Mario Kart 64 and Mario Kart: Double Dash, but worst then Mario Kart Wii.

You think it's going to sell over 10 million copies? o.O

Mario Kart games continue to sell well after the launch, so its very well possible, especially if nintendo actually gets decent marketing.