Here are the individual character posters for the Avengers flick (although as you can tell by the banner image the Hulk and Thor have still to be released). Apart from Iron-Man the costumes are more in line with the Ultimate comics version rather than the classic Marvel but I'd put money on an Ultimate Iron-Man suit appearing at some point. The use of the Ultimate costumes doesn't really come as a great shock when you consider Sam Jackson was cast as Nick Fury (who the Ultimate Nick Fury was modeled on) and although they're not every bodies cup o tea I dig them and think they look great. (if you've seen the post credits Captain America 'Avengers trailer' you'll know that Thor also sports a more Ultimate's looking costume.)
And if the wait is just to much for you check out the Ultimate Avengers animated movie.