My take: Epcot was the Imagineers' sop to Walt Disney's (the man, not the company) dream of the REAL "Experimental Prototype Community of Tomorrow."
They knew Walt's dream was highly implausible if not outright impossible, so they built E.P.C.O.T.* to represent the technologies and knowledge Walt's dream city would need to come to fruition. (Besides, he was gone and didn't sign the paychecks any more, so they could basically do what they wanted.)
That turned into Edutainment, which worked just fine until sponsorships started drying up and the education system started teaching tests and the Internet made available to everyone everything, everywhere, all at once (not a plug for the similarly named movie).
So as the Epcot kids started growing up, they got bored with Epcot -- having seen it all before -- and asked the serious question, "Why is there a Disney park without any Disney in it?"
And the managers, who by now were all MBAs instead of artists and imagineers, agreed, seeing $$$ in adapting the park to the new audience.
So if they're re-re-reimagining Horizons into Test Track v3, no biggie. If they throw a couple of Cars cars in there, well, it's a natural fit, isn't it? Or if Tesla buys into it with some money and cars, what would be the harm?
Of course, if Tesla joins in, they'll have to make Goofy the main character.
* Every Penny Collected Off Tourists