A few points to make here after reading all these posts: (Working two miles from the Indianapolis Motor Speedway, yes, I am biased)
1) People say Indy Speedway does not belong in tomorrowland. However, ethanol is used exclusively in the Indy Racing League. This is home-grown fuel and the thing of the future. Therefore, if you focus on that, it fits in quite well.
2) NASCAR is bigger then IndyCar right now in the US, but in Indianapolis I hear the Indy 500 is still bigger. I am going to the Brickyard 400 this year and I'll see for myself.
3) I don't know if I can stand a Cars theme.
4) For a kid (and some adults) the speedway is an awesome attraction. I admit that I don't ride it every trip as the 1000 miles I drove to get there is enough. I still enjoy walking by though. I don't think the Magic Kingdom would be the same without it.