I'm going for Venom too the theory that Spider-Man finds the symbiont and becomes the black spidey...fights sandman as the main villain through the movie and gets rid of the symbiont later in the movie and that's when Eddy Brock takes him over seems very likely
cause it was claimed that the next villain would stay almost completely human through out the movie which means he probably is a monster...so I think that puts away the theory that harry would be it...altho I have my doubts about it...