The Peoplemover (as it was called in a previous life) ran until Tomorrowland went under a huge refurbishment I think. TL closed in like 1996 or so and reopened a couple years after that and the Peoplemover was gone. However, the tracks weren't empty.
In 1998, Disney introduced Rocket Rods. It was a very fast paced ride that used the same track as the Peoplemover but you rode it little 5 person rockets that accelerated quickly. The problems with Rocket Rods was
a) It broke down way too much
b) The peoplemover track itself was not built for a high speed adventure. The Rocket Rods had to slow down at each turn because there was no banking. This caused a wear in the tires very quickly and it was $ to replace.
So Rocket Rods retired after a couple years. There has not been anything on those tracks since, although there have always been rumors (Incredibles Pods, Star Wars Speeder bikes, TRON attraction, etc.) but none of them have been confirmed or even remotely close to being confirmed.