One Piece: Stampede is an upcoming movie scheduled to be released in Japan on August 9, 2019. It will commemorate the anime’s 20th anniversary.
The movie takes place during the Pirate Festival Expo, “made by pirates, for pirates”, where pirates all over the world, including some of its most infamous ones, join in for a big treasure hunt to find a lost treasure, this time the treasure belonged to none other than Gold Roger!
The film takes place after the Whole Cake Island Arc, as Luffy and Sanji are shown with the bounties they received from its events.
One Piece: Stampede will have the main cast and two unpublished and original characters created by Eiichiro Oda (Notably, the two new characters are named Buena Festa and Douglas Buller):
Straw Hat Pirates:
• Monkey D. Luffy
• Roronoa Zoro
• Nami
• Usopp
• Sanji
• Tony Tony Chopper
• Nico Robin
• Franky
• Brook
Special Guests:
• Douglas Bullet
• Buena Festa
• Donald Moderate
The Worst Generation:
• Trafalgar Law
• Eustass Kidd
• Killer
• Jewelry Bonney
• Capone Bege
• Basil Hawkins
• Scratchmen Apoo
• Urouge
• X Drake
Seven Warlords of the Sea:
• Buggy
• Boa Hancock
• Dracule Mihawk
Marines:
• Smoker
• Issho
• Borsalino
• Sakazuki
• Hina
• Koby
• Helmeppo
• Sentomaru
• Monkey D. Garp
• Sengoku
Revolutionary Army:
• Sabo
• Koala
CP-0:
• Rob Lucci
Other Characters:
• Marshall D. Teach
• Ann
• Crocodile
• Alvida
• Mr. 3
• Foxy
• Wapol
• Bartolomeo
• Cavendish
• Perona
• Gol D. Roger
You can watch the official trailer on youtube here.