Possible huge spoiler for
The Amazing Spider-Man 2:
There’s a bunch of high-quality production photos out, most of which we've seen before, but the one big exception is the photo of a wall with a giant honking “Sinister 6” written on it. There have been quite a few rumors that the famed criminal sextet would take on Spider-Man in one of Marc Webb’s movies, with the most common speculation suggesting that this film would put the pieces in place for a full-fledged Sinister 6 team-up in the next film. That would rather explain the glut of apparent villains in this one, considering this movie already features Electro, Rhino, and both Norman and Harry Osborn, not to mention Colm Feore in an unspecified part that has frequently been connected to the Vulture. Now, this photo shouldn’t be taken as definitive proof of anything, as it’s quite possible this is just the production team messing with the fans, but it’s at least some kind of acknowledgment that the Sinister Six is on the minds of those actually making the new Spider-Man movies.
Source.