A Venom spinoff would be awesome. I'd love to see that. I know the Venom Saga from the 90's cartoon is on DVD and those were some cool episodes. Though if a Venom spinoff did happen, Sam Raimi would have to direct it. Though did Carnage ever fight Venom, I don't remember if they did and I only seen the 90's cartoon. Never read a Spiderman comic so I'm not sure. But that would be a great way to see Venom again because he is my one of my favorite Spiderman villains. I had hoped to see more of him in the movie, but oh well.
Anyways, I just hope there is a Spiderman 4. With all the success of 3, I can't see why not. But I heard that if Sam doesn't direct, then the cast won't want to return. It makes sense.
And just for a tidbit of useless info, the Japanese did a TV show version of Spiderman in 1978. It was live action and get this, Spiderman had a car (The Spidey Machine), and he had his own MEGAZORD. He even had some kind of morpher on his one arm. You can watch episodes on Youtube by just searching Spiderman and scrolling down a ways. I watched an episode and it's kind of hard to explain.