The superhero world is moving into the 21th century, finally. In the world of comic books, it seemed to be an unwritten rule that lead heroes had to be Caucasian and male. Few comics featured woman as heroes and even fewer female leads received mainstream attention. Even fewer still were anything other than Caucasian. However, things are changing quite a bit. Marvel recently announced that Thor is getting a new look and a new sex. Thor will be a woman. The second announcement is a change to Captain America. Steve Rogers will no longer don the Captain America mantle, instead the shield will be taken up by African-American Sam Wilson, also known as The Falcon.
I agree the story needs to make sense, the idea won't be embraced unless there is a real and logical (in terms of comic book superhero logic) story to follow.
The outfit will likely be skimpy/sexy, the comic book world is taking baby steps in the right direction but ditching scantily clad female characters would be a giant leap. Here is the concept art for the new Thor: http://time.com/3001549/marvel-thor-female/
The amount the character's attitude changes will likely depend on the story arc the writers take. There will likely be some changes in the persona but hopefully they can remain true to the world that surrounds Thor as a character, if that makes any sense.
I think this is a big step in a good direction, but like Byony, I want it to work with the story. If a decent explanation can be made, then it kills the character for me. I also hope that new characters can be introduced that have a more varied background.