Kraven the Hunter and Mysterio are being eyed for solo film projects by Sony Pictures, according to The Hollywood Reporter. They will follow the planned Silver & Black and Venom movies that the studio already has planned, the latter of which will reportedly feature Carnage as a villain.
Although Kraven and Mysterio would seemingly be more apt as antagonists in the planned Spider-Man: Homecoming sequels, THR names those two as planned projects - with the on-again, off-again Sinister Six being "shelved."
The article also gave more insight on the precise nature of Sony's deal with Marvel Studios' for the Spider-Man film rights and Spider-Man: Homecoming. While Sony retains the film rights and receives all revenue from the movie itself, Marvel - in exchange for making the movie - can use Spider-Man in their own Marvel Studios films, and also reap any rewards from non-movie uses of the character such as in merchandise and video games, which Marvel retained the rights to.
"It really came down to me telling Amy [Pascal, former Sony Pictures head] in her office that I think the best thing for this character is: Sony has the rights, that's not changing," Feige said. "Have Sony pay for the movie, distribute the movie, market the movie. Just let us make the movie and incorporate him into our universe."
Tom Holland is reportedly contracted for two Spider-Man: Homecoming sequels, but Sony also intends to use him in their Spidey-related movies just as Marvel Studios has with Captain America: Civil War and the upcoming Avengers: Infinity War.
"Marvel is so good at [working around your schedule]," Holland said. "They're very respectful of your life, really. They understand that you have to work on other movies, and yeah, they try and fix it up so you can work."
While Robert Downey Jr.'s Iron Man has been front-and-center in Sony' Spider-Man: Homecoming marketing, he isn't scheduled to return for the sequel - although as part of Marvel's deal with Sony has another another "to-be-determined Marvel character" to appear in the planned July 5, 2019 sequel.
Speaking of schedules, although the Silver Sable/Black Cat film Silver & Black has no announced release date, Sony is expected to begin shooting the film this fall.