Technically no one has seen the SM4 script because it hasn't been finished, not to mention that Raimi has expressed interest but also has expressed interest in "The Hobbit" as well and they'd conflict in shooting schedules. Also Raimi hasn't exactly been asked back.
Is it possible for a return of Venom? Of course, especially if all the internet speculation and rumor is in fact....well fact, and the GG statue is appropriately named, that certainly didn't stop the comics. Take this into account through for lack of development of the Venom character, Raimi has been more than vocal about his distaste for Venom, he felt he wasn't deep or interesting enough to bring to the big screen, if you look hard enough you'll see he has said this multiple times. Take into account the horde of fans almost demanding Venom on screen and the fact that Avi Arad said they'd use a darker costume and darker tone when SM2 came out you could imagine that the Symbiote storyline was planned but the Venom one was a fan's choice add on. The original Symbiote storyline spanned a lot longer than some remember including an end of Parker's original dealings with the suit that had nothing to do with Venom. It was the symbiote's aggression and escaping the Baxter Building (they just replaced Reed with Connors) that resulted in the showdown in the church, it disguised itself as the Red/Blue suit to trick Peter into bonding with it and was removed thanks to the church bell. When Brock got the suit it he didn't go after Spidey right away but built up his body and trained for his attack. They could have easily done the symbiote storyline and ended SM3 with the disgarding of the suit. Venom saved. Since Raimi, Maguire and Dunst's contracts were all up they could have in theory just said "throw Venom in for the fans".
Venom's background is based on Brock's background. That's the character development. Venom's bonding shows Brock's hatred for Parker mixing with the Suit's hatred with Spidey. If they explain how Brock hates Parker/Spidey...then done. If they show why the suit might feel rejected and go after Spidey....then done. Then they background'd Venom....whether they did it well or not is another story.