I am well aware of WDW's current capacity nightmare. As an aside, the post you linked too is quite obsolete as WDW's attendance actually declined last year. But let's even say that was an anomaly and the trend of increasing attendance will return: the parks that exist today are more than capable of being able to accommodate this rising attendance. The problem is the lack of attractions, not a lack of parks. The WDW parks are completely underdeveloped, particularly outside MK. MK is by far the smallest of the four parks, yet it has by far the most rides, and the most overall attractions (and Disneyland is much smaller and has even more), which just goes to show that the other parks can fit significantly more attractions.
There is a lot to unpack there.
First, I would hardly call it "quite obsolete" because of a 1% decrease. No projection is going to be perfect, nor all circumstances entirely predictable. If you notice, there is also a very prescient bit in there about "coming additions".
We have found out a hell of a lot more about those additions since then (namely, SWL and the boutique SW hotel, not to mention new attractions for MK, etc). For all we knew at the time we were going to get X-Wing and TIE spinner rides for Star Wars and nothing else of significance anywhere else. It remains to be seen what Pandora did for 2017 - though on that count, I do think it probably evened out the parks a bit, more than anything else, I don't expect any huge increase, but I'm sure that it was enough to put those projections back on track.
But SWL? We are pretty much getting the "best case" realistic scenario there could be. It's going to drive massive attendance to WDW, which is going to make the overall capacity issue even more dire than the post I referred you to said.
Second, I have to ask - have you ever
been to Disneyland? If you have, then you should know that making such casual comparisons as you have here is completely daft when it comes to discussions like this. You are right, Disneyland is crammed solid with attractions. Attractions with entrances nearly on top of each other. Attractions with lots of outdoor bare-bones metal switchback queues. And the ones that do have long queues (a couple are comically long) aren't for aesthetic purposes but for necessity to move people to show buildings outside of the park perimeter.
They are never going to pack the Florida parks nearly as densely as Disneyland. Nor would we want them to. That doesn't mean that there aren't more expansion pads, or even that as fans we wouldn't want them to further expand each park. Or that they won't. But given the additions/replacements in the pipeline, and the fact that Disney continually wants to demand more and more days from visitors to keep them from splitting up their trips, the next step after the current additions are done is indeed a fifth gate.
