Judging from this thread (and many others I've read) Disney has managed to alienate some of its most loyal repeat customers. Many are planning to go back less often. Some are going to try other destinations while taking a "wait and see" attitude. Some are done with Disney altogether, at least for now. And FP+ seems to be the main culprit.
How many businesses can afford to piss off their most loyal customers? For now, Disney appears to be getting enough first timers to make up for any shortfall. But how is that sustainable in the long run? Just how many new, untapped markets are there? Maybe they need to start organizing tour groups among the eskimos.
Also, ask yourself how many first timers are going to become repeat customers? The flexibility of the legacy Fast Pass system was one of the key reasons that Disney earned our loyalty in the first place. Now that it's gone, I can't see FP+ encouraging many of the first timers to come back.
Also, it's no coincidence that most of the WDW repeat customers are people who live in North America, particularly the east coast. When you can drive over, or take a short, relatively inexpensive flight, that certainly encourages people to come back. If you alienate many of those who live close to Florida, how are you going to make up for it with people who are flying in from overseas? For many of them, WDW is a "once in a lifetime" experience, or something they can only afford once per decade. Again, just not sustainable.
And all this is happening at a time when Disney has more competition than ever, including a cross-town rival that just keeps building new, cutting edge attractions. It really is too bad Disney spent a fortune on a new IT and reservation system, rather than new attractions. If they had done the latter, we would be beating down their doors for years to come, instead of complaining on message boards and rethinking our travel habits.