It seems doubtful. If you're already planning on spending a few grand on a trip, another $100-$150 in parking probably isn't going to be killing your plans. In fact, with the annual rate of admission price increases, you could be looking at a similar problem by pushing your stay out if you waited - especially if you're a family of four or more.
This really just feels like an easy and cheap way for Disney to turn those security gates with guards from a cost to a revenue generator while providing nothing to any of the guests impacted by the charge that they weren't getting before with their nightly rate.
I think they're just gambling they can get away with this knowing that while it'll make people who notice unhappy, it won't make them unhappy enough to significantly change their behaviors... Which feels more like the kind of frustration you expect to feel towards a car dealership when they get your car color in stock from another dealer but "discover" it comes with a $500 package already installed that you didn't want - not the kind of crap you want to deal when going on vacation to a premiere destination but I guess we should stop being surprised by this kind of stuff. After all, every other resort in town pulls this scam so why should they worry about their reputation?