Just received this offer in the email, and it looks to be open to everyone. Simply stay 4 nights between January 1 and March 31, 2012 at any IHG hotel worldwide, and earn 5,000 bonus Priority Club points. You must register prior to completing your 4 nights in order to qualify, and no retroactive points will be awarded for stays prior to registration. Only one room per member per stay will be awarded the applicable bonus points.
To register, go to the generic IHG offer registration page, enter your Priority Club number or email, and then enter the promotion code 2183. This offer is fairly easy since it is awarded by nights, not stays... so there is no need to hotel hop in order to meet the requirement.