If the Marines were to make a appearance, I hope they're little more reserved, in comparison to James Cameron's grunts.
I found them alittle too chest pumping and in-your-face. Hopefully they're alittle more calculated and cold, which would be a slightly interesting change from years of appearances from them in other various mediums (novels, games, comics).
Also, please, please mix up their combat gear. Please, give them a whole new modern look. Again, their appearance is old-hat. Move on from Aliens for the love of god. lol.