things did change a lot.
But there are still many doesn't. For instance, Ethernet, serial communication, RS485, RS422, CAN bus, etc. Those industry protocol and hardware probably still will last a very long time. Mach 2 and 3 are more on the industry and hobby side, which probably means a Win 7 64 bit support is a good decision.
As long as used/aged machines are still available, this won't be a big deal. However, when all those aged machines are out of service, Win 7 64 is the only way to go probably in next few years. Or try the open-source Linux. (Is there a 64 bit of Linux for CNC purpose? Just curious.)