Lets face it there will eventually be a clone of at least part of Carsland in wdw. Wether it's a carbon copy, or it's just a copy in its theme is yet to be decided. I could see TDO not wanting to build RSR because its so similar to test track and instead wanting to do something different, but having the development costs payed for already and knowing how to improve a little bit on the operations aspect of RSR is probably to good of a deal to pass up.
Now lets get to one of the main reasons we'll see Carsland in Orlando, tourists!!! Not only domestic ones but international ones as well. WDW is the number one tourist destination on earth, being a CM it's eye opening at how many international travelers go through there. TDO has really been playing up to the international crowd lately, avatar isn't that popular here but internationally it's huge, and having Carsland would certainly help draw them in.
It would also draw in more domestic tourists, if a new to disney family looks at a Disney vacation between WDW and DL they will probably pick WDW because it looks like there is more bang for your buck. It has double the theme parks, 2 water parks, larger entertainment district, golf courses, resort specific activities, oh and it's neighboring theme parks are pretty good. (Let's face it TDO loves having potter down the street, the amount of business it brought them probably payed for some of NFL) Oh and after that new disney family goes to WDW and experiences everything it has to offer, there will be plenty of DVC rooms disney is waiting sell them.
Raven you hit the biggest nail on the head as to why disney will build Carsland in WDW when you said, if you want to see Carsland just skip WDW for a few years to save up for a trip to DL. That's the last thing disney wants its guests to do and they will go to great lengths to keep that from happening.
