Along with a 3DS firmware update (which doesn't do anything interesting), a new patch sent to 3DSes yesterday closes up the , in Mario Kart 7. The patch is required for online play, so you will no longer see miraculous leaps forward on that particular course. The glitch still shows up intime trials.
Now you have only your own driving skill to rely on in Mario Kart. Well, that and blue shells. Actually, mostly blue shells. Now, you have only the random chance that you'll get a blue shell and not be hit by a blue shell to rely on.