If we take away Japan it has (probably - with digital) already happened!
North America
1 Mario Kart Wii - 15.84
2 Mario Kart DS - 9.79
3 Mario Kart 64 - 5.55
4 Mario Kart 7 - 4.66
5 Mario Kart: Double Dash!! - 4.12
6 Super Mario Kart - 3.54
7 Mario Kart 8 - 3.09
8 Mario Kart: Super Circuit - 2.62
Europe
1 Mario Kart Wii - 12.82
2 Mario Kart DS - 7.56
3 Mario Kart 7 - 3.80
4 Mario Kart 8 - 2.00
5 Mario Kart 64 - 1.94
6 Mario Kart: Double Dash!! - 1.77
7 Mario Kart: Super Circuit -1.64
8 Super Mario Kart - 1.24
Japan
1 Mario Kart DS - 4.13
2 Super Mario Kart - 3.81
3 Mario Kart Wii - 3.79
4 Mario Kart 7 - 2.63
5 Mario Kart 64 - 2.23
6 Mario Kart 8 - 1.23
7 Mario Kart: Super Circuit - 0.99
8 Mario Kart: Double Dash! - 0.87
VGChartz database: http://www.vgchartz.com/gamedb/?name=mario+kart&publisher=&platform=&genre=&minSales=0&results=200
