I really don't think there's any doubt as to whether or not SWL will be a ginormous success -- I think it's a safe bet to say it will be. But I really don't see them having the luxury to do much elsewhere in the park other than Tomorrowland anytime within the next few decades at this point. The motor boat cruise area is hardly big enough to do anything significant with IMO unless they remove the subs and Autopia when they get around to Tomorrowland, which I kinda hope they do.
There are many purists who do not share your sentiment of Toontown. It's very take it or leave it to me. I like it because my kid loves it over there, but otherwise, I think it's kind of an obnoxious plastic-y remnant of bad 90s theme park design which luckily didn't have much of an impact on the park other than that little pocket. I dig the idea behind the storyline, but the aesthetic -- while fun to look at initially -- is far more dated looking than the stuff built in the 50s IMO.