I believe this is coming w/ the "DirectX 11 Patch" .. I'm not positive about that, but I thought I saw mention of it somewhere by Crytek. Considering the first "Crysis" had x64 bit mode, and then "Crysis Warhead" had x64 bit mode added w/ a patch, I feel sure that "Crysis 2" will get x64 bit mode with either a patch or the directx11 enhancement patch.
What they NEED to do, is make x64 bit mode for "multi-player", they never did in the past because of extra work needed to be done to allow x64 bit mode players to connect to 32 bit mode servers, but it can be done. The easiest thing for them, would be putting up x64 bit servers, but that would be a big FAIL. Just do some extra tweaking and make them compatible w/ each other.
Truthfully, x64 bit mode servers might have less hackers... =0