The following probably won't happen, but back at the mariokartwii.com forum, I did speculate on some stuff for the next Mario Kart installment...
[collapse=Roster]
Four characters per weight class, except for the Cruiser and Metal weight classes, which have two characters each; 40 characters total. Cruiser consists of large-sized middleweights, while Metal consists of medium-sized heavyweights.[/collapse]
[collapse=Retro Tracks]
Shell Cup
3DS Daisy Hills
SNES Choco Island 1
Wii U Thwomp Ruins
Wii Toad's Factory
Banana Cup
GCN Mushroom City
N64 Koopa Troopa Beach
GBA Sunset Wilds
3DS Rock Rock Mountain
Leaf Cup
Wii U Dolphin Shoals
DS Mario Circuit
SNES Bowser Castle 3
N64 Choco Mountain
Egg Cup
GBA Snow Land
Wii Daisy Circuit
3DS Wario Shipyard
DS Bowser Castle
Lightning Cup
N64 Wario Stadium
Wii U Bone Dry Dunes
Wii Moonview Highway
GCN Rainbow Road[/collapse]