At the moment, iTunes 10.6.3 is not yet available through the standard Software Update method on Macs, though it should be soon.
Note that, contrary to the deep 3rd-party social integrations that iOS (and soon Mountain Lion) has gained as of late, Ping is still alive. Still, following Tim Cook’s comments at the ATD Conference, the social failure can’t possibly have much of a future ahead of itself.
When asked if he would kill off the music-based social network, Cook said “some customers love it, but there’s not a huge number that do, so will we kill it? I don’t know. I’ll look at it.”