I bet it's Tatooine. It makes sense for a number of reasons:
1) It was a featured location in 4 of the 6 films. If any one place says "Star Wars" it's that one.
2) It's depicted as a polyglot of cultures, truck-stopping aliens, charming rouges, dangerous gangsters, imperial officers and Jedi all could be seen walking about there. Not really true about Hoth or Endor. This not only widens storytelling possibilities, but it leaves wiggle room for new Episode 7-9 species / vehicles to be dropped in once they are know to the world.
3) While you could say that Courasant or possibly Bespin are just as wide open for diverse storytelling, that location is too much of just another clean shiny Tomorrowland. WDW already has one (or two if you count Future World). The resort needs more weathered, aged, escapism - Tatooine is ideal for that kind of placemaking.
4) While it kinda sucks that a podracing attraction would make the lame Episode 1 the new headlining E-ticket for a park saluting the greatest of Hollywood, it has the potential to really fit cutting edge theme park tech: Think building your own pod (a la TT2.0), variability from a real for real race against other racers (if its one big video game simulator) or, while we're dreaming, a Kuka arm attached to Radiator Springs Racers... Could be mind blowing.