CS6 is EOL, end of Life, there is no more upgrade path. Only CC subscriptions are possible.
What RAF files? You should check with which versions the CAMERA, not the file type will be compatible.
What operating system are you running?
There is no upgrade path from CS5 to CS6. You can buy CS6 at full price if you call Adobe. But you're buying a product almost four years old which will never be updated. And it will probably not run well on the newest Windows or Macintosh operating systems. The phone number is in the last paragraph of this page:
A much better choice is a Creative Cloud subscription.
CS6 has reached end of life. If you still wish to buy an unsupported application you’ll need to call Adobe directly.
That said, are you sure you shouldn’t be in the Photoshop forum?
Photoshop CS5 might open more flavors of .raf than CS5, but are you certain it would open the ones produced by your camera? It would be a shame to go down that expensive road for nothing. InDesign does not import .raf at all.