I had never pondered that. I'm so used the multiverse shows bringing new characters into the fold.. Didn't arrowverse do that to get Supergirl into the main universe? I could very easily see them push the Spidey we know out of the main universe as a way to let Sony do what they want and close his chapter in the MCU.
I much prefer this idea:
Arrowverse did Crisis on Infinite Earths to condense most of the disparate DC/CW shows into a single universe similar to the comic event from the 80's. Although, even at the end, it acknowledged that the multiverse was forming again to let Doom Patrol, Titans, and Stargirl still exist in separate universes.
Technically, all options could be on the table for Spider-man with a multiverse. The could cast a new Peter Parker for the Sony-verse, keep Holland's Parker around for a special occasion in the MCU, bring in a live-action Miles, do even more of the animated ones, etc. Not every thing has to be tightly connected, but the door can be left open for cross-over potential. They could even go the James Bond route with just using new actors for the roles while maintaining the same basic continuity.