I haven't seen a projected release date for a Windows x64 version of Firefox. The best I can offer is that a release will occur 12 weeks after it hits the Aurora channel.

Have you tried Waterfox?
http://waterfoxproject.org/

I'm on Win 7 x 64 and out of general interest tried Waterfox 9(x64) with the same profile, add-ons, history etc as my Firefox.

No problems but there must be an element of risk and I couldn't really see the point with no support and no speed increase I could detect in normal browsing.

At this stage, I don't think you are missing anything with Fx 32.