Giamatti revealed that he's signed a multi-picture deal with Sony that will see him through the next film, although he's unsure if he'll be needed for the fourth, which is expected to hit theaters in 2018. The plan at this point seems to be that each sequel will build to the formation of the Sinister Six, it's just of when they will show up and who will comprise its villainous members. Rhino will most certainly be amongst them, and we can probably expect Jamie Foxx's Electro to be in there as well since the actor has spoken openly about it. The director Marc Webb has had quite a bit of fun teasing their arrival, as well.
For what it's worth, Giamatti doesn't sound like he has any inside information, although he could just be playing coy and not wanting to spill the beans. Although if we look at this logically, if Giamatti isn't confirmed for the fourth film, then that means we should see the Sinister Six turn up in the third.
The Amazing Spider-Man 2 opens May 2nd 2014, followed by The Amazing Spider-Man 3 on June 10th 2016.
