Just throwing this out there.... Why doesn't Disneyland need new walkways and a hub replacement? Isn't Disneyland
I.E. Disneyland! Not nearly as big but has a quarter more attractions and it handles crowds pretty well considering how small it is. If MK the kept tortuga tavern, diamond horseshoe, keel boats, swan boats, explorer canoes, skyway, and the freakin always closed noodle station open as well as open a major attraction every 7 years MK would be able to engulf the crowds no problem.
Disneyland certainly has more attractions, and I do wish that we had that many (though due to aesthetic differences between the parks, and the fact we have four parks, I doubt we'll ever see that number). And there's no doubt that adding attractions, and in particular opening up the restaurants that are currently closed most of the time, would help - but its not going to magically solve the problem. Solving it entirely through new attractions would need to see at least a doubling of the current offerings. And if you think that if WDW did that (especially rapidly as most would suggest) and attendance wouldn't nearly double I think your mistaken. (Incidentally Tortuga Tavern, Diamond Horseshoe, and Noodle Station have been open a lot more than usual in the past year with Tortuga being open nearly all the time.)
I would also add that a major new attraction every 7 years sounds reasonable. Consensus would say that the last major addition to MK was Splash Mountain - which didn't involve the closing of other attractions. By this logic then the MK is only short two major additions in 96, and 03. This was the end of the Eisner era, its not surprising. Additionally the entirety of AK was being built in that time - resources devoted elsewhere. The next year following that pattern would be 2010 - FLE arrived in 2012 and 2014. 2 years late. Yes some would argue that this does not really constitute an expansion (because 20K used to sit there 2 decades ago) or a major addition (because the two rides aren't "E-Tickets"). I can see that logic but considering that area of the park was doing nothing for 20 years (half the life of the park), forgive me for counting it. The capacity of all the new walking areas, queues, rides, attractions, and restaurant, are at least double or triple whatever the capacity was for 20K.
My most important point: If you've been to Disneyland anytime after 12:00PM its clear that it does need more and wider paths (especially in tomorrowland, adventureland, and New Orleans square, a bigger hub (although their hub packs in substantially more standing room than our current design), as well as bigger bathrooms. Attendance continues to go up there and its getting squeezed. Granted - keeping the pathways small adds to the charm, but it can be a nightmare trying to get where you want to go -- especially in the evening, with nearly every path becoming one way and traffic slowing to a crawl. I was trapped near the matterhorn for about 30 minutes before fireworks because essentially every path leading out of the area was closed either for safety or for crowd control. The reason Disneyland has not expanded its pathways (recently) is there is just essentially no way to do it without major construction work throughout the park that would have to see the rebuilding of most everything a couple feet back from where it currently exists now. And Disneyland is getting a Main Street bypass as well, for the exact same reasons. At the MK, expanding the hub is a simple as bringing in a bit more dirt and pouring the concrete. It might happen one day, but it would be a mammoth undertaking and I'm not very sure its feasible. Their best strategy is to draw people to DCA and keep attendance moderated with a slew of blackout dates on tickets and passes for all but the most expensive of passes.