Sony has announced on the PlayStation Blog that the Starhawk Public Beta will commence this Tuesday.
All PlayStation Plus subscribers and all participants of the Private Beta who haven't erased their Private Beta files will be able to log onto the beta on January 17. On January 31, anybody with a Beta Key they received in copies of Uncharted 3: Drake's Deception. On February 21, anyone with a PlayStation Network account will be able to join the Beta.
Sony at this time has not announced an end date to the Public Beta.