^ I think Fox have to do no more than have a DD project in development to retain the rights to him and associated characters. So they could basically pay their janitor to write a script with crayon on tracing paper and have no intention of ever making the thing and keep Marvel from getting Kingpin back. Bastards.
Of course, even if Marvel got the Kingpin back, that's still no guarantee that Sony would pay to use him for a Spider-Man movie.