User blog comment:Jacknapier10/Which characters cannot appear in the Marvel Cinematic Universe?/@comment-5350299-20140428113836/@comment-3317214-20140429232918

Well, villains tend to go with the heroes they face off with most. Which is why we see Lizard, Electro, Green Goblin, Doctor Octopus, Sandman and Venom in Spider-Man films, because they're primarily Spider-Man villains.

Rhino is primarily a Spider-Man villain, so Sony's got him (he shows up in Amazing Spider-Man 2). Kingpin, we know is attached to Daredevil, and now that he's back at Marvel Studios, so is Kingpin. Hydro-Man's primarily a Spider-Man villain, isn't he? And although Klaw first showed up in Fantastic Four, he seems to be sort-of a villain for anyone, so I wouldn't be surprised if he's at Marvel.