Amazing Spider-Man 2 already has Electro, Rhino, and the Osborns in it, but a new viral marketing Tumblr page for the movie hints at even more:
Other highlights included a preview of a flight harness for the military and significant advancements in robotics by the head of the engineering division, Spencer Smythe.
The flight harness is obviously a reference to The Vulture, and Spencer Smythe created the robotic Spider-Slayers in the comics.
Back in June, Ace Showbiz reported that Colm Feore has been cast as Adrian Toomes (The Vulture):
The Vulture is said to team up with other villains Rhino, Electro and Green Goblin “to form the first four members of the Sinister Six,” a group of supervillains that will likely turn Spidey’s world upside down in the upcoming film.
If their report is true, it definitely would make sense with the fight harness comment that The Vulture would show up in the movie as well…