1) I'm afraid they'll update or "modernize" his costume, which is purposefully meant to evoke the image of the American flag, by making the red aspects (gloves, boots, stripes) maroon or burgundy like they did to the Superman costume in SR so that Cap will look "darker and more mysterious" even though he's not meant to be a dark/mysterious character.
2) I'm afraid that the film just won't do well at the box office regardless of how well written, acted, directed and marketed it is because Cap stands for Truth, Justice, & The American Way, the last one which will make it difficult to market him to the global market and will just turn off cynical audiences who don't care about being patriotic or loving their country or whatever.
And now for something completely different - does anyone else here think it's really stupid to put Wonder Woman back in the Invisible Jet for the new movie that Joss Whedon's supposed to be making for her? (forgive me if I ranted about this a few pages ago; my memory's been shot lately)