This is a completely different situation than Fox. In the case of 20th Century Fox, that was a company looking to sell. Disney having already made such a transaction have ensured that they can't buy another major Studio. Otherwise they're violating monopoly laws. That just simply can't happen again. We can argue that Sony. Is not doing well financially, but that's not true. You can say they have nothing outside of Jumanji and Spider-Man, but they also have many successful movies like Once Upon a Time in Hollywood. Not everything is all about the major blockbusters. We'll have to see what other things like Ghostbusters Afterlife and stuff do, And I'm not going to argue that Sony is the second or even third biggest Studio out there, but every time the topic comes up it gets shut down. If they sell eventually it won't be to Disney. We also don't know anything about how the Spider-Man rights actually work if such a scenario materializes, so really it's rampant speculation. For all we know if Apple or Amazon or somebody else buys the studio from Sony, then the rights may very well stay with whoever buys it.
I get that fans want these things. I get the some of the stuff that fans have wanted him happened. But that doesn't mean everything fans want to happen will happen. There are real things preventing such a transaction from occurring. The only way I see Spider-Man reverting back to Marvel is if Disney outright buys the IP from Sony. I don't see any other scenario in which that happens, and something tells me Sony is going to put a price tag that Disney won't pay for one character. Especially not when they already own the most profitable part of that IP, that being the merchandising rights.