The Venom storyline is going to be more of an introduction, isn't it? My prediction: Jameson's son is going to bring it back from his moon trip. Hop from him to Parker at a news conference. Parker runs the symbiote through the paces over New York. Spiderman uses it to stop the Sandman (after previously getting his ass whoop by Sandman w/out symbiote). Spiderman gets rid of it because during the fight with Sandman; the symbiote wants to kill Sandman. Symbiote passes to Topher Brock who is like-minded (ie bully, callous, etc). Movie ends.
Spiderman 4 - VENOM LIVES!