tweeted that Marvel Studios is currently giving their pitch out to writers for a War Machine film. Previously it had been rumored that Marvel was hoping to make spin-offs from the Iron Man and Avengers series. Don Cheadle ruled himself out of the Avengers films because of War Machine's close connection with the Iron Man franchise. I wouldn't be surprised after Iron Man 3 we see a couple of War Machine films before we ever get Iron Man 4.
Of course the Nick Fury/SHIELD film has been in development for years. Black Widow is also on the horizon for a spin-off. Now that Disney has bought the Iron Man rights from Paramount I expect we could see them mining the Iron Man well for more features. It wouldn't make sense to see the movie become reality until 2014. So it could be just in early stages at the moment. There are still a massive amount of spin-offs and originals in development like Ant-Man, Black Panther, Iron Fist, Doctor Strange, Sub-Mariner and Hawkeye.