For years the 5D2 was the camera to aspire to, and even now with the latest releases it is still the camera to compare the very best with, so that still makes it an excellent camera to use.
Quite honestly, I don't need the improved AF of the 5D3. It would be nice to have, and my inner techno-geek would love to have the latest, greatest shiny toy, but will it improve the AF success rate of my 5D2 which is about 99% in a studio? Not really.
Do I need more megapixels? Not really.
Do I need to buy new lenses, new radio triggers? Not really.
For someone moving to FF the 5D2 offers the best value for money.