There is already speculation, now that Captain America: The Winter Soldier has been such a huge blockbuster- That Marvel Studios will do another Iron Man movie. It may take place sometime before Avengers 3, or it may be the 1st movie of Phase 4. Robert Downey Jr has said he would do a fourth movie, IF Mel Gibson was the Director. Hey, Say what you want about Mel's private life and personal problems. He is a great Director and has the Oscars to prove it. I'm all for another Iron-Man movie!
Here are my reasons why Marvel Studios will make an Iron Man 4...
1. Iron Man 3-
It was a movie that made a billion dollars worldwide but still pissed off a lot of fans because the main villain: The Mandarin turned out to be a fraud, played by an actor named Trevor. They started to fix this with the "All Hail the King," One shot- where it is learned that there is a REAL Mandarin.
2. Hail Hydra!
It was learned in The Winter Soldier that Senator Stern, not a big fan of Tony Stark and his suits, was in fact a Hydra Agent. What of Justin Hammer? He was a close friend of Sterns. Was he a Hydra Agent too? Building suits for Hydra? He also had the MKII suit to play around with and upgrade. What about other HYDRA Villains like Madame Hydra or Baron Zemo? (I'd add Baron Strucker to that list but he will be in Avengers: Age of Ultron.)
3. Advanced Idea Mechanics-
The rival to Hydra and the real Villains of the previous movie. Are they still around and plotting their next bid at World Domination? Killian may be dead but there are still other bad guys that work for A.I.M. (MODOK or perhaps the Scientist Supreme?) These would be good villains for a 4th movie right?
And a Bonus Reason...
Tony Stark needs to build more suits and these suits need to be awesome and indestructible, not the stack of empty beer cans that fell apart every time they got hit. He is using Hulk Buster in AoU as well as a MK42 looking suit. We need to see armor that can take a licking and... well you know.
Now it's your Turn...