I can answer this a little better since I just got back earlier this week. Unless you knew previously (which most of us do), you'd never know there was a race track at the Magic Kingdom exit. It's gone. As you leave Magic Kingdom, the first turnaround that would have put you back into the parking lot without having to go thru the entrance plaza is no longer available. I was incorrect in my earlier post that it had been torn up...but, there are cones across it, so you can't use it. The second turnaround for return to the Magic Kingdom on the left side is still available. Of course, with that one, you would have to go thru the entrance plaza again and show your receipt. Also, there is construction going on at that spot with concrete barriers that I would think would limit your visibility making that maneuver. I think there's a short catch up lane on the left side to make it a little easier, but be very careful if you use that turnaround.
As mentioned earlier, there's a lot of construction going on in that area so don't count on this info to remain correct for any period of time...