Seeing as Downtown Disney has a Rainforest Cafe, I'd find that highly unlikely. Besides, the food there is pretty terrible. You're paying for the experience and spectacle.
Toothsome would be pretty cool, but there's a lot of candy/sweets places at CityWalk already (It's Sugar, and Sparky's is now mostly all candy... plus the upcoming VooDoo). I do believe it'd be a different enough brand, and I personally hope it comes here, but I could see reasons not to bring it (not to mention where exactly it'd go).