I'd guess they'll mess with the Brock character and the origin of the symbiote as well. I can see it coming from space, but the Brock character as played by Topher Grace being true to the comic origin? Can't see it happening.
Simple PLEASE NOT THIS IS MY TAKE:
Brock is already established as existing doing work for the Bugle in Spider-Man 1. Now we get a face to the name, after Spider-Man is out in a new black suit, and he's not sure how he gets it. Doc Connors explains it's a symbiote, rah rah rah, Peter got it after coming into contact on a field trip or working with J.J.'s son or somthing. Peter also inadvertantly costs Brock his job by getting better shots of Spidey. Peter gets taken over slowly by the symbiote, goes to kill Sandman, bells ring at the church, suit falls off, Brock who was inside ready to kill himself because parker/spidey cost him his job gets it, and then hell breaks loose. Then with the added threat of The Hobgoblin, it gets so much better.