In an interview conducted by Nintendo Power magazine, 3DS producer Hideki Konno spoke about how Nintendo wants to introduce "new elements" to the game, although further details will have to wait until next month:
Now that Nintendogs + Cats is done, I've been able to spend more time and energy on Mario Kart development. We really want to bring a bunch of new elements into the game, and I'm really looking forward to the time that I can announce what those elements are. Perhaps we'll be able to talk in more detail at this year's E3 event.
Konno has previously stated that the development team will be looking into ways to balance out the power items in order to keep everyone in the race until the very end. Whatever new changes we'll see in the series, we can be fairly sure that items such as the crowd-dividing Blue Shell will probably retain its place in the franchise's arsenal of crazy weapons.