In an alternate timeline, Robert Downey Jr. and Chris Evans would be fighting over civil rights while Andrew Garfield swings around them singing tra-la-la and offering snarky one-liners.
Buried in the massive leak of internal Sony Pictures documents, The Wall Street Journal has found emails between Marvel Studios and Sony over collaborating on future Spider-Man movies. According to the report, "extensive discussions" went all the way up the chain to Sony CEO Kaz Hirai and Walt Disney CEO Robert Iger. Specifically, Sony Pictures Entertainment co-chairman tells a colleague that Marvel wanted to include Spider-Man in Captain America: Civil War, which kicks off so-called "Phase Three" of the Marvel Cinematic Universe on May 6th, 2016.
Imagine Marvel producing a Spider-Man trilogy while Sony retains "creative control, marketing and distribution"
Curiously, according to WSJ, a separate email between Pascal and Sony Pictures president Doug Belgrad discuss a scenario where Marvel produces a new Spider-Man trilogy but Sony retains "creative control, marketing and distribution." That first part — "creative control" — seems more wishful thinking that reality; Marvel Studios is notoriously controlling over its creative vision (cf. Edgar Wright's Ant-Man) and Sony's recent track record Spider-Man films hasn't hit the same creative or commercial highs. While Spider-Man is a Marvel Comics character, Sony has owned the exclusive film rights for years.
The Marvel and Sony talks eventually broke down, according to WSJ. In fact, as of late November, executives were planning a "Spidey summit" for January to discuss future plans. As it stands, Drew Goddard's Sinister Six is planned for November 16th, 2016 (about six months after Captain America: Civil War) followed by Venom in 2017, and The Amazing Spider-Man 3 in 2018.
No clue if Marvel Studios also reached out to Fox for similar discussions. Fox owns the movie rights to the X-Men universe (which includes Deadpool and the term "mutant") as well as Fantastic Four.