Adobe announced on 3/21/12 the availability of a public beta for Photoshop CS6. Just like Lion (and the forthcoming Mountain Lion), Photoshop CS6 will require a 64-bit processor.
This change will kill support for running older 32-bit Photoshop plug-ins. It doesn’t matter if the Mac is physically booted into 64-bit mode or 32-bit mode, as long as it has a 64-bit processor. Photoshop CS6 requires Mac OS X 10.6.8 or later.