Electro (Jamie Foxx) is the main villain in The Amazing Spider-Man 2. But other villains will show up. Green Goblin is one of them:

The Amazing Spider-Man 2 Official Trailer

Plot:
“Peter Parker (Andrew Garfield) runs the gauntlet as the mysterious company Oscorp sends up a slew of supervillains against him, impacting on his life.”

And thanks to this new poster we may have a closer look to Green Goblin’s face:

(Click on the poster to enlarge.)

There’s no more doubt: Harry Osborn (played by Dane DeHaan) is Green Goblin!

Release date: May 2, 2014.
:)