This news article
on Thom Hogan's site is essential reading if you intend moving to Apple's next 64-bit OS now or in the future, or if you will upgrade to a future Windows 64-bit OS.
The summary: software, apps and even files that are written in 32-bit code will not be able to be used or opened in the new 64-bit operating systems. Some software that is currently 64-bit uses 32-bit code behind the scenes.
I already keep an old Mac to run Epson Scan software. When it comes time to upgrade my current Mac Mini, I will probably keep it to run my non-subscription Adobe CS6/LR6, plug-ins and other software that is not 64-bit compatible, and disconnect it from the internet to avoid any malware concerns.