There's a lack of female superheroes on films. And it seems that the tend will continue. The only solo female hero movie in production is wonder woman. Gal Gadot was chosen for the part. But the fandoms are very skeptical about her. They predict that it will be a failure as the Green Lantern movie.
Scarlet Johanson as Black Widow was well structured as a character. Appearing on multiple films is filling the gap for a female representation but remains as a secondary character always.
Xmen series tried to give storm a more important role on x2 and x3 but forgot about her later. With the new series first class and days of future past they are trying to give a current female villain a more importan role with Mystique. I think this occurred because of the fame Jennifer Lawrence had acquired and thus the character is being overrated.
Actual images of Avengers 2 show a Scarlet Witch dressed like a got girl. Well it was logical that Disney wouldn't use any of SW sluty attires. We must wait to see how they develop the character.