They may not, but someone else definitely will. The only game I know of which can be exploited and can earn you online-only achievements for a game where the server is offline, is FIFA 11. It's an in-game glitch which is allowed due to poor coding and it doesn't take any software manipulation to perform.
Other than that, I don't know any other game and with this one in particular, chances are someone will dob you in.
If my search serves correctly, it looks like you've already been reset in the past. Why run the risk of a permanent profile suspension and even a possible console ban? If this is you, so be it. But don't risk losing hundreds of dollars of stuff for a few achievements.
Last edited by iBuzz7S; 03-22-2013 at 08:39 AM.