Well, it supposedly takes place in the Dragonball universe, so that'd make Goku still a child, and it'd make Piccolo... LORD PICCOLO.
The original Dragonball universe was decent, but I'm sure it will be bastardized by this movie. They should have just ruined something that already sucked, Dragonball Z.
Even then, his opponent would brush it off and giggle. Then Goku would spoend 3 more films going SSJ XXVIII. At which point, his hair becomes a giant dong and he rapes his opponent to death with it.