Sony clearly knew what direction they were going to be taking Marc Webb's Spider-Man franchise before the first film had even been released, given the heavy foreshadowing that occurs, hinting at all three of the villains who would ultimately appear in the movie. Paul Giamatti's Rhino is referenced mid-way through the film, when Gwen Stacy is in Oscorp Tower, and we can see a hologram of the Tree of Life, referring to a number of different animals that may be suitable for cross-species genetic experiments. Most of the creatures shown are fish, birds and insects, but there's one that sticks out like a sore thumb, and that's a rhino, an obvious reference to Spidey's famed villain, as well as confirming the fact that it was clearly already planned out for Rhino to appear in The Amazing Spider-Man 2.