Yesterday's entirely expected news of more Amazing Spider-Man sequels and a pair of spin-offs in the shape of Venom and the Sinister Six kicked off what will inevitably be a hotly contested debate for who would be best for the incoming characters to populate those movies. Some might say that Venom is tied up, with Eddie Redmayne a strong suggestion considering how close he came to being cast instead of Andrew Garfield as Spidey, but the Sinister Six movie requires a little more thought.
We've already seen fairly definitive villain performances in existing Spider-Man movies, with Willem Dafoe's Green Goblin and Alfred Molina's Doctor Octopus at the top of the pile, and the Sinister Six spin-off obviously offers an opportunity to see at least five more. Electro is likely to return, since he's been a stalwart member of the team in the comics - which could well spoil how his story ends in The Amazing Spider-Man 2 - but we will also get to see new takes on Doctor Octopus and Sandman, as well as portrayals of Kraven The Hunter, Mysterio, and Vulture.
So, who should be in the running to fill out Spidey's rogues' gallery? As with The Avengers, the key issue here is balance, so it's not merely a question of casting good actors, or ones who possibly look like their potential roles, it's also important to consider how the cast would fit together, and how Sony can make the right blend so they don't end up making a movie that stumbles into the same issues that Spider-Man 3 did with its bloated cast of villains.
As already alluded to, Electro has played a major part in the Sinister Six history, and it's unlikely that Sony will recast the villain for a Sinister Six film just two (or possibly three) films after his first appearance in The Amazing Spider-Man 2. Foxx certainly looks the part, and if he is to return it would suggest that Sony feel particularly good about his performance in the upcoming sequel.
There is of course the possibility that the Spider-Man writers will choose to go with a later line-up of the Sinister Six perhaps including Rhino - but it's unlikely that both Electro and Rhino will see the forthcoming sequel out to the end without dying, and with that in mind, it's the classic line-up that we are looking at here.
There's also the possibility that Sony will be liberal with their definition of who the Six are, and will extend the team to include Green Goblin (which would of course make the team a limited version of Goblin's Sinister Twelve,) but then there's little chance Sony will take the chief villain of forthcoming Spider-Man movies (presumably) out into a spin-off in anything other than a supporting role. So maybe he'll set the group up (in place of Ock,) but it would be wrong for him to appear as a main character.