I wouldn't pay for the promise of 64bit support in something that sounds like it's hard/impossible to implement because of PatchGuard. There have been ways around patchguard, but since it's not exactly something MS supports (in other words, requires exploit kinda code) I wouldn't want to depend on a piece of software that has to use such tricks.
At the same time, I feel it's a shame that MS hasn't provided official & clean hooks for some of the stuff that PatchGuard makes impossible. 64bit drivers already have to be signed, so it's not like anybody could just write a driver and subvert the system protection.