Capcom will release Resident Evil 6 on October 2, 2012, and a newly revealed Xbox 360 Achievements list (via Xbox360Achievements.org) offers some hints for what is to come. The majority of the cheevos are related to campaign progress and completion difficulty, with the rest filled out by collectibles, kill goals, and special actions, such as countering an enemy's attack three times in a row or maxing out your unlockable skills.
Interestingly, none of what's listed appears to connect with the game's high score-focused Mercenaries mode, though I'm guessing kill targets like "defeat 500 zombies" can be influenced by your performance there. There are also a handful of secret Achievements, presumably story-related. None of the revealed descriptions are very specific in terms of the story, but the usual spoiler warnings still apply.