I can't see a theme park based solely on SW being very sucessful. On the other hand, it'd be cool to see maybe a SW themed section at Disneyland or something. Similar to how it is with the Indy ride, only with maybe a ride, and a restaraunt, and a giftshop, etc.
I'd personally like that a lot better than a whole theme park devoted to SW. As much as I love SW, I can't see spending a few g's just to go to a themepark that is nothing but SW. Whereas I can see spending money to go to Disneyland with an SW attraction, because there is more to do at Disneyland.
The reason that other attractions, like Star Trek exp, get made is that it isn't a park by itself. Its one very small portion of the Hilton in Vegas, where people go on vacation anyway.