Starting June 20th through August 31st, the Sip n' Sail Promo will be running for cruises from "Summer 2018 through Spring, 2019". I don't have anything more specific than that at this moment. If you book a mini-suite or full suite, you also get one free specialty dinner.
2017: 2 down, 2 to go: Pacific Princess & Regal Princess
2018: Crown Princess, Emerald Princess & Azamara Quest
2019: Star Princess, Royal Princess & Azamara Journey