With Andy Serkis directing the sequel, it is rumored that Venom 3 will be a part of Marvel Studios, the MCU and will be produced by Kevin Feige.
The Lords of the Long Box YouTube Channel claims insiders have filled him in that Venom 3 will be an adaptation of the "Maximum Carnage" comic book storyline featuring Venom, Carnage and Spider-Man.
It's also claimed that more than likely Venom 3 will be PG-13 within the MCU as it features Spider-Man.
The YouTuber also claims the rumor surrounding the billion-dollar clause in the Sony and Disney contract surrounding Spider-Man is "nonsense" (worth a mention is that the rumor doesn't matter now as Far From Home has made over a billion at the box office).
Venom 3 coming to the MCU?
Regarding whether the Venom 3 rumor is true is unknown, but it does fit with previous information that offered Sony wants to further connect their Spider-Man spinoff universe to the MCU and even the Avengers.
Presently, Sony retains the film rights to Spider-Man and the related characters, while Disney retains the merchandising rights surrounding Spider-Man. Disney and Sony's original deal is said to feature three Spidey MCU movies and appearances, so assuming this info is legit, a new deal is or has been made. Tom Holland has appeared in Civil War, Infinity War and Avengers: Endgame and was featured in Homecoming and Far From Home, with a Spider-Man 3 MCU movie underway (we can also assume Holland will get a new contract).
There have even been rumors offering that Kevin Feige wants to use Norman Osborn for a potential Dark Avengers movie or even as a big bad, but this YouTuber seems to debunk those rumors questioning why would Feige go with a character owned by Sony as a major villain.
What is also rather interesting regarding Venom 3 is that Andy Serkis has connections with Marvel (Klaue) and his expertise with motion-capture work would actually be a huge benefit for something like a Maximum Carnage (assuming Serkis would stick around for Venom 3).
Venom 2 is said to be filming soon for its October 2, 2020 release date, which sees Tom Hardy return as Eddie Brock paired with the symbiote and Michelle Williams back as Anne Weying. The flick may also feature Woody Harrelson as Carnage.