New characters? Nope.

Since it launches with smash first and Mario kart is not to next year they probably have something big planned for it. They cannot just have a little something planned for their biggest series. Maybe it will have characters from other games in it. That Rosalina reveal video was all smash but you never know with maybe that was a hint to what's to come in Mario kart.

lol, it's true.

Mii costimes and/or vehicles parts

I'd like Samus' arm cannon to let you target and fire on a Kart. Kind of like the bomb. Or maybe a EMP, ice beam, absorb item with the grapple beam.

It would probably be a good idea to make the next Kart technically Smash Bros. Kart since then we could at least get some new looking levels.

If they can put a freaking mercedes in the game than I don't see any problems with new characters.

My feelings exactly.

I'll only accept maybe a cameo, or karts with Metroid or Zelda themes... and honestly, that's even going too far.

One and a half month later ...

Welp... That means that Samus is going to eventually get confirmed as well!