Wild guess time:
The three remaining new tracks are Rainbow Road, Bowser's Castle and Tropical Freeze... and for the next trailer, they'll show the Tropical Freeze course, and reveal Diddy, Dixie, Cranky and/or Funky. The second half of the trailer will be the new Bowser's Castle, wherein they'll reveal Bowser Jr., Birdo, Dry Bones and Dry Bowser. They'll also show bits of N64 Yoshi Valley and GCN Sherbet Land, and the "Speaker" and "8" items will be detailed.
Yeah, there is always a DK track and a snow track or combination of those both...
Mario Kart 64 = DK Jungle Parkway & Sherbet Land
Mario Kart Double Dash = DK Mountain & Sherbet Land
Mario Kart DS = DK Pass
Mario Kart Wii = DK Summit
Mario Kart 7 = DK Jungle & Rosalina's Ice World
Mario Kart 8 = DK Tropical Freeze?
There is also always a retro Bowser Castle track...
Mario Kart DS = GBA Bowser Castle 2
Mario Kart Wii = GBA Bowser Castle 3 & N64 Bowser Castle
Mario Kart 7 = GBA Bowser Castle 1
Unused Bowser Castle tracks:
SNES Bowser Castle 1, 2 & 3
GBA Bowser Castle 4
GCN Bowser Castle
DS Bowser Castle
Wii Bowser Castle
3DS Bowser Castle
They will probably follow the tradition and pick
GBA Bowser Castle 4. DS Bowser Castle would be a nice surprise.
Wild guess time:
Star Cup (new tracks 9-12)
Sunshine Airport
Bone Dry Dunes
Dolphin Shoals
Electrodrome
Special Cup (new tracks 13-16)
Cloudtop Cruise
DK Tropical Freeze
Bowser Castle
Rainbow Road
Leaf Cup (retro tracks 9-12)
3DS Piranha Plant Slide
DS Bowser Castle
GCN Sherbet Land (Sunshine Airport departures board destination)
N64 Yoshi Valley (Sunshine Airport departures board destination)
Lightning Cup (retro tracks 13-16)
DS Tick-Tock Clock
Wii Grumble Volcano
3DS Music Park
N64 Rainbow Road
Mario Kart 1-7 tracks &
Mario Kart 8 tracks