While aboard Liberty Of The Seas last week one of my friends on the bar staff told me they would be getting the booze packages too. He said they were going to start offering it in February on their 4 and 5 night cruises. So, it seems that within the span of a few weeks RCI has broadened the plan to cover everything except 3-night cruises. Initially it was to be for 7-night or longer cruises.
Also, I can confirm that the price includes the 15% tip so when they say $55 per day it won't be $55 plus 15% per day.