I'm tending to agree with you. Our family was at DLR this past summer when Pixar Pier opened (I know not the same as SWGE but it certainly drew the crowds) and even though Incredicoaster was a 6 hour wait and the other attractions on the Pier and elsewhere in DCA had huge waits, DL park was DEAD. If you spent the day there instead of DCA, you had quite the magical experience.
I can see how this could be for WDW too. For the opening and immediate days following, HS will be nutso, but the other parks will be more in line with normal Sept crowds. There may be some people who get fed up with the crowds at HS and spill over into the other parks but I think most will feel that they only have this opportunity to experience SWGE when it has first opened and they will hang in there despite high crowds.
Hope those of you who are disappointed and cannot move your trips are still able to have a great time. As I said we were at DLR when Pixar Pier opened. That was NOT by choice. Disney sprung the opening on us like 6 weeks or so before our trip AND lifted the blocked out AP's just a few weeks before. We had planned the dates we chose for like 9 mos because a couple tiers of AP's were blocked. We were unable to move our trip so we went and made the best of it. We DID actually choose to go into Pixar Pier on opening morning (and we despise crowds!) because it opened on our last day there and we realized this was our only chance to see it anytime in the near future. It was crazy, crazy, crazy but also, really fun and exciting and there was an energy that isn't normally there. I would not have planned that experience cause my instinct is to avoid that kind of thing but we did have a great time despite that craziness!