The events of "Iron Man 3" with the twist on the Mandarin being just an impostor undoubtedly left a bitter taste in the mouths of Marvel fans. Short of a confirmation, the Marvel One-shot served as a teaser that the story has not ended.

Notwithstanding the well-publicized impasse between Marvel Studios and Robert Downey, Jr. there are still strong reasons to believe that RDJ might return for an "Iron Man" feature.

First of all, there is a real Mandarin based on the Marvel One-shot, "All Hail The King" which has Ben Kingsley portraying Trevor Slattery in prison. The full developments from the Marvel-movies Wiki:

"Over the course of their discussion, Norriss (Jackson) produces a gun hidden in his camera and takes out the guards in the cell as well as Trevor's 'butler', Herman, Trevor manages to get a gun and aims it at Jackson, but Jackson disarms him and aims the gun at Trevor's head. But instead of killing him, he reveals himself as an agent of the reclusive Ten Rings, and informs Slattery that there is a real Mandarin, who wants to get even with Trevor for appropriating his name. While Slattery struggles to comprehend this turn of events, Noriss initiates a prison breakout for him."

Since there is a real Mandarin, what would prompt Tony Stark to break out from his self-imposed retirement? Events in 'Captain America: The Winter Soldier' further revealed the story of Tony Stark's father and the fact that he was killed by HYDRA agents.

HYDRA turns out to be so much more powerful and influential, and there could be links between the Ten Rings and HYDRA. One example from Moviepilot: "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. Did he copy Starks' Technology and help Hydra build 'Ultron?'"

Justin Hammer was in the same cell as Trevor Slattery and he was present when he was broken out of jail. It is believed that he might have escaped as well.

All these plotlines may culminate in "Avengers:Age Of Ultron" but the Ten Rings issue will probably be resolved in another film-none other than Iron Man 4. As always, everything revolves around Tony Stark, and he alone can make the resolution.