The following document explains:
Because Adobe hasn't officially announced official CS6 pricing and availability dates yet, your best bet is to wait until there is an official announcement on pricing and availability.
The upgrade policy for CS6 was posted yesterday:
If you purchased Creative Suite 5.5 or a Creative Suite 5.5 component on or after March 26, 2012, you qualify to receive a complimentary upgrade to the equivalent Creative Suite 6 product at no additional cost when it becomes available.
See link above for for comprehensive Adobe upgrade info or the link below for CS6 specific details.