Sony got a little ahead of themselves in regards to setting up their Spidey-verse, so I think it's safe to say that whatever they were planning before THE AMAZING SPIDER-MAN 2 hit theaters, could be altered. Still, with the release of SPIDER-MAN 2 on Blu-ray/DVD, commentary and behind-the-scenes video have shed some light on what was in store. For one, that Norman Osborne was planned to return in a Spidey flick (as his head was cryogenically frozen). As for the rest, most people have already guessed it given the clues during the end credits, but a user was goodly enough to upload the words straight from the filmmakers' mouths.
Here's the video, via Amazing Spider Man:
As Webb notes, nothing has been decided so I imagine it's all up in the air at this point. It's unfortunate to say that THE AMAZING SPIDERMAN 2 put a bad taste in my mouth, regarding the direction of the series. While I felt the villain was weak in the first entry, the dynamic between Peter Parker and Gwen Stacy was above and beyond what Sam Raimi was able to accomplish with his trilogy. Now that Stacy's out of the picture, it's going to take a hell of a lot to pull me back in. Let's see what Drew Goddard can do with the Sinister Six come 2016.
THE AMAZING SPIDER-MAN 3 is scheduled to hit sometime in 2018