I don't know if it would have sunk the company. The fact is that EPCOT, the actual city, was still in the very early stages of planning when Walt died. If you look at the initial plans for what became Disneyland compared to the final park, the two are very, very different. Remember that Walt was never one for pushing things out before he felt they were ready. Heck the facade for the Haunted Mansion was completed at Disneyland for years before the ride finally opened. I don't know the modern process, but back then, you had a central idea and then it was designed and redesigned over and over in order to solve as many issues as possible and to make the final product as perfect as possible. Walt was also not one to stick with something if it became clear that it was simply not going to be feasible. It's impossible to say whether or not EPCOT, the city, would have been completed had Walt lived another decade or two, simply because society and the world economy changed so much during that time period. The remainder of the company simply decided to scrap it immediately, since it was so early in the process and they no longer had Walt to oversee the project. I don't blame them. I wish that there was some alternate reality where we could see what would have happened, but sadly, that wasn't to be.
From what I've gathered in my reading, the company didn't want to admit right away that they weren't going to build EPCOT, the city, since so much of the cooperation they received from Florida and its industries had been predicated on what had been presented to them by Walt. Once they got the MK up and running and it was a humongous success, whenever they were asked about EPCOT, they would say that it was still on the table. They thought that people would eventually forget about it. They didn't, which is why the second park was called EPCOT Center and was touted at the time as part of the eventual EPCOT city. It was only a couple of years later that the Eisner regime came in and EPCOT, the city, officially died once and for all. Future World was very much tied to Walt's original ideas, since it was predicated on being a showplace for emerging technologies that would impact our lives. Mixed in with this were history lessons about man's progress in relation to each of the topics covered in Future World pavilions. The only minor exception was Imagination, which was still driven by the idea that nothing is created without first using your imagination. It still tied in to the central theme of EPCOT Center.
I guess that's a long-winded way of saying that EPCOT Center wasn't a slap in the face to Walt's dream. It was a way of honoring his dream and his enthusiasm for futurism, whilst taking into account the reality that, without Walt, they wouldn't have been able to even think of pulling off such a massive idea as EPCOT, the city. To be fair, WDW did accomplish many of the ideas that came out of the EPCOT project, including the way it is governed, its development of alternative transportation systems, the development of alternative fuels, the way waste is handled, controlling systems via computer from centralized locations, etc. It has strayed away from some of those as the decades have passed, but only because of the change in focus at the top and the departure of "Walt's people" from positions of power and influence.
Eisner did try his hand at building a planned community, Celebration, but it wasn't successful. Why? He wasn't Walt, though he desperately wanted to be. They didn't take into account many of the issues that popped up with controlling an entire town. Now, Walt would have faced these issues as well and may well have also failed, but we'll never know.