All of Apple's competitors are listing their ship times with the new 6-core as the end of March. I wouldn't be surprised to see Apple announce something around then with immediate availability, rather than fill their store with a product that won't ship for a while.
Thank you Peter for your optimistic projection!
Right now there are 20 models from 12 manufacturers that are offering <1 week ship times on high-end (pre-built/turnkey) Windows 7 based machines featuring the i7 980x Extreme Edition hexacore/12-thread single socket (3.33Ghz, 3.60 w/ Turbo Boost) 32nm chips, at price points very competetive with the existing dual socket MPs.
http://www.intel.com/consumer/shop/core_i7_extreme.htm
Nevertheless I am a Mac loyalist and would rather have a Mac Pro as my long term investment in a desktop PC. I am dismayed with Apple's sense of timing after seeing how quickly the Windows-based competitors are in step with the "official" Intel rollout date (last Tuesday) of the new process silicon.