So if luffy fights Big Mom after challenging her
and wins he would have to return to fishman island and make it his territory so that would extend the story and like every island arc there would be a plot on the island so we could assume that arc would take more than 1 year (about 48 chapters) (including the way to fishman island and then the plot on the island) and then luffy would have to go from fishman island all the way to raftel adding extra chapters for repeating all the journey from fishman island
So we could say the Straw Hats will start the New World once again after returning to fishman island
so assuming that I'm guessing One Piece has more than 4 years left
[video=youtube;dBDXcdo5k-Q]http://www.youtube.com/watch?feature=player_detailpage&v=dBDXcdo5k-Q[/video]
So we could say the Straw Hats will start the New World once again after returning to fishman island
so assuming that I'm guessing One Piece has more than 4 years left