Sony Studios owns the rights to the Spider-Man universe, and they have every intention of keeping it separate from Marvel. Sadly, this most likely means we probably will never get to see the web-head join the Avengers any time soon (or will we...?). However, Sony does plan to build a huge Avengers-like universe with the characters they have. But Spidey's just one guy, how could they build a multi-film universe?
Sony's plan continuously seems to change since the first two Amazing Spider-Man films didn't seem to deliver, especially to fans. There was talk of having a solo Venom film, but since then the idea has been shelved. But who knows, Venom is popular enough to have his own film.
Venom was horribly mishandled in Spider-Man 3, when he was a throwaway third act villain with no time to develop much (if any) real backstory. We, the fans, need Venom done right.
Now for the hard part: which Venom should they go with? Hopefully it's the 616 (regular comics continuity) Brock, who's a bodybuilding maniac, bent on destroying Spider-Man because he ruined his journalism career. They might also go with the Ultimate universe iteration (which, in fairness is what most Marvel Studios films and this round of Spider-Man films are drawing from) in which Eddie is more of an anti-Peter Parker.
We've cast for both versions accordingly, the hulking brutish Brock, as well as the squirrely, vengeful, Ultimate universe style Eddie as well.The Spiderman 3 Venom actor was of course Topher Grace, but these actors would expertly fill the role. Who would be your pick?
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616 Universe Venom - Lesnar is probably the only guy who actually looks like the old McFarlane drawings of Eddie Brock, but he'd need to take some acting classes, and maybe grow a mullet.