I have pretty much no interest in another Sonic Kart Racer, but wouldn't be opposed to seeing them try again. I still want a Racers Megamix more than anything, basically an arcade racer in the vein of Daytona or Sega Rally, but with tracks and cars from all their games.
It'll never happen in a million billion years, so Mario Kart it is. Maybe they can win me over with their next attempt.