According to Comic Natalie, and OVA of a prequel to the One Piece manga is in the works.
The OVA will be available in a limited release of 3,000 through a promotion with House Foods in Japan. The manga version of the prequel will appear in the 53rd volume of Shonen Jump, where the series is serialized.
If you happen to live in Japan (or will be there for the movie’s opening), 1a copy of the prequel manga , volume zero, will be given to the first 1.5 million attendees of the 10th film Strong World), opening Dec. 12.
See a trailer for the film here: (One Piece Film)