Yes it is planned, but as yet there is no release schedule for a 64-bit Windows build.
Probably not. For Audacity the performance bottlenecks are usually “CPU single core speed” and “disk I/O”.
It may also be worth pointing out that one can run a 64-bit version of Windows and reap significant benefits from that, even with a 32-bit Audacity build. Specifically, this will allow Windows to manage lots of RAM, and allocate it to Audacity and other programs more readily, speeding up the overall system, Audacity included.