Assuming Disney and Marvel stay broken up, I actually could see a few things happening as far as the Peter Parker/ Spiderman films go
1) The status quo left from SMFFH will basically still be the same, so the notion that that may be retconned ain't gonna happen. My guess is references to Mysterio will be minimal.
2) We'll likely see a Spiderman/Peter Parker who's lost alot of the advantages he had in the other MCU related films, i.e. Stark tech, Avengers status, and will now probably make his own suit ala the Raimi and Webb films. My guess is that Ned will become his tech guy .
3) We may start to see "classic" Spiderman elements that some fans have complained about i.e. more overt references to Uncle Ben, A Spiderman who has to stand on his own two feet, JJ and the daily bugle, probably the introduction of the Osborn family and Norman as his new Stark like mentor
4) Aunt May won't be dating Happy
5) We'll see Venom , Dr Ock, Kraven , etc and move toward the Sinister Six vs Spiderman film.
The question mark to me is the status of the MJ / Zendaya character. She's basically a MCU creation if you believe the rumors. If so, that character could get yanked... though that doesn't mean Zendaya can't appear in the next film .
My guess is that if Sony wanted to keep her , they could say her character is indeed now Mary Jane Watson as opposed to Michelle. There would be fans who are upset by that but the GA would go along with it since alot of people think she's Mary Jane anyway.