Allyn Gibson wrote:
I would question whether or not Sony would have the rights to Miles Morales as a specific character in the first place. The movie rights were sold to Columbia (who was then bought by Sony) back in the 90s, and I harbor doubts that the contract would be worded so vaguely that Sony would automatically hold the rights to a character created within the last five years.
This is likely a huge reason.
I am not a lawyer, but I would imagine the contract Columbia originally signed probably included the entire Spider-Man universe, past, present, and future. This would allow them to make films based on upcoming Spider-Man comics that hadn't been released at the time of the comics. The fact that Miles Morales wasn't around at the time doesn't matter, because he's part of the universe.
Although I agree that it would be cool for a spider character to show up in the Avengers as a huge eff-you to Sony.