Because Batman Begins did such a good job of establishing Bale as Batman they could shift focus to The Joker/Harvey Dent.
Man of Steel needs to establish Cavill as Superman. Now, I hate to say this but I think it's more important for Cavill to have charisma and a screen presence than to be a great actor. This isn't Daniel Day-Lewis performing Abraham Lincoln. From what I've seen of Cavill he appears more charismatic in interviews and being charming around fans than his actual performances in movies.
I think with a good script/direction he has a chance to exude his natural charisma which would help his performance.
Brandon Routh was similar in that regard. He did better with public relations and press with representing Superman offscreen than onscreen.
I think the focus of Man of Steel is on Kryptonians VS Humanity, and whether the world is ready to encounter aliens. The SDCC trailer had alienation as a key theme.
That being said, I think the main focus will be split between Crowe, Shannon and Cavill, and I'm banking on Shannon being the standout performance. Hopefully this film's 'Heath Ledger' type.