first of all, what are you planning to do with your system. if its video editing and all that workstation stuff, id think about x79 or getting a i7 3770k. if its purely gaming, there is no reason to go beyond a i5 3570k
second thing is that a i7 3770k is faster than a 3820, but less upgradeable. assuming that intel does release a ivy bridge e, it would be the same thing as regular ivy bridge, but with more cores.
and if you are going the 3820 route and thinking about a upgrade later on, have you considered the likely hood of you actually upgrading your system?