What would prevent Disney from making more $$ off of a Star Wars land, not to mention having a big draw for WDW?
If they build the Star Wars land, or 1/2 park, by around the time frame of the new movies (2015, 2017, 2019 and possibly on and on), then they could host special premieres at this park. Plus, they could put it into the actors' contracts that they have to make a set number of appearances at Star Wars land over the next ten or fifteen years.
Those legions of drooling fans you referenced would probably be more than happy to migrate down to Orlando every couple years for a Star Wars convention on the property.
I doubt if anyone would argue against the fact that WDW has ride capacity issues, especially during peak times, and that park attendance is sluggishly growing, putting more pressure on aging rides.