I don't think the idea of Disney owning a track is necessarily a bad thing. I think the planning, location, and series involved are not well thought out. If Disney had chosen a different area of the property (I'm not sure where that would be) and developed its own infrastructure (roads, parking, permenant grand stands, etc.), things might have been better.
Also I think that if Disney had tried to get the Winston Cup boys instead of the IRL and the Trucks they would have packed the stands every year and there would still be racing there.
As we all know Disney can put on a really good show and I think this would have been true for a NASCAR race also. Plus they might have gotten new people to Disney that might not go there if it wasn't for the race.
Do I think there will be any professional racing there again? Probably not. There were too many complaints about the traffic and noise that the regular WDW guests had to deal with. Again. if it was in a different location, this would not be a problem.