I hear they are filming part 4 and 5 simultaneously. Like Lord of the Rings.
Why stop there? Why not make part 6, and include the Sinister Six?
Spider-Man has trouble dealing with one bad guy at a time, even in the comics, so how would he handle six at once? It would not only be a great finally, but could include some fan favorites that might not make it otherwise. Plus, if Tobey and the rest retire from the Spider-Man universe after this film, it would be a major send off.
movie Mysterio's costume:
I have an idea how to explain, in the movie, Mysterio's odd costume.
May contain spoilers about Mysterio
In the comic he tells how he disguised himself as Spider-Man, creating devices to make him look like the real Spider-Man and give him Spidey's powers.
But once he had framed Spider-Man he decided to create a superhero persona to swoop in, stop Spider-Man and save the day.
He designs his costume sort of mimicking Spider-Man's.
Everything Spider-Man can do he can do too, artificially.
His bubble dome head is based on Spider-Man's one way mirrored eyelets. His smoke gloves are based on Spidey's web shooters (in the movie it would be more like he invented an artificial way to do what Peter can do naturally).
His checkered costume could be based on Spider-Man's design too.
What if Mysterio's costume was made like Spider-Man's for the movie, the raised web design would just be made black but still raised and made more like checked lines.
Maybe if someone could photoshop a Spider-Man movie costume (making the red greed, and darkening the spider-web design.)
Anyway, his outlandish costume would be because he was just trying to upstage Spider-Man