All depends on how you use it. If you buy cameras, CS6 will read future ACR (currently 8.2) although no "enhancements" will be included. CS5 will be stuck with 6.7 forever.
Look at the list of CS6 enhancements and see if you might use them. Beware that CS6 uses the video card more heavily and therefore at least a moderate card is needed. 3D requires at least 512 meg VRAM.
Hope this helps.
If you are a photographer and are shooting raw files, the rendering and performance improvements in ACR hosted by CS6 amply justify the upgrade costs.
If you do ANY stitching for pano, then I would definately say yes!!! There are so many more great features in CS6.