You're probably familiar with DeHaan from Chronicle and Lincoln. He's joining Andrew Garfield, Emma Stone as well as Shailene Woodley (Mary Jane) and Jamie Foxx (Electro). The movie is currently in pre-production and there hasn't been too much information released, aside from the updates in casting.
As the pieces are starting to fall in place, in terms of the cast of characters, it won't be long until everyone begins speculating on the direction of the sequel. It's already been lightly thrown around that the third movie could head towards the Death of Gwen Stacy storyline. We'll have to wait and see if there's any truth to that comment.