At least not for a while and very likely not in 2011. Firefox 8 is going to be the next trunk (nightly) builds starting July 5th and there is currently no expectation that 64-Bit Windows support is going to part of Firefox 8. For those interested in what is going on behind the scenes, you can follow these tracking bugs:
One of the main issues is currently the developmental builds for Windows 64-Bit Firefox only support 64-Bit plugins. Because not all Windows plugins provide a 64-bit version, 32-bit versions would also need to be loaded. See Bug 595053.
