7. Agent Carter
People have suggested that if any Marvel woman is going to get a spin off it will be Scarlett Johansson's Black Widow. However, with the superspy Avenger's appearance in Captain America: The Winter Soldier in combination with her role in Iron Man 2, Marvel seem more keen to use her as a supporting player crossing over between various movies. Instead, the first Marvel woman to get her name as a movie title in the MCU has been Peggy Carter, the British agent from the first Captain America, whose Agent Carter short was released as an extra on the Iron Man 3 DVD. Agent Carter has won enough positive notices from both critics and fans for Marvel to consider making further adventures for the character.
How likely is it? At the moment Marvel are pretty committed to their schedule of two feature films per year and that schedule is all booked up for the next two or three years. Agent Carter is only likely to occur as a feature if Marvel branch out into more and lower budget films. Further shorts would seem like a more likely option, but once again Marvel are currently only developing one short per year so it's a pretty competitive field. The final possibility would be to follow-up current success Agents of S.H.I.E.L.D. with another TV series focused on the earlier, wartime era of the company's characters. Either way, it's likely we'll see Carter again at some point, but probably not so likely as the lead in her own film.
Who should star? Hayley Atwell's performance in both Captain America and the Agent Carter short is a lot of the reason why the character has been this popular. Atwell is a rising star with plenty of big screen potential. If a feature or a handful of further shorts were produced then she would be perfect to continue the role. Were Marvel to push Agent Carter as a long running TV series, though, Atwell's blossoming movie career may make her unavailable for such a regular small screen commitment. In that case, a British actress with TV action experience should be found to fill in. Former Bionic Woman Michelle Ryan might fit the part.