Hello fellow straw hats the theory iam about to is what I call the end or finale of one piece.
Here is the theory it is that when we think about the end about one piece end which is foreshadowed to be attend of the new world i.e on the mysterious island raftel which is supposed to be the last island on the grand line. Here is the idea i don't think it is .
I think the one piece which is suppose to be on the rafael is only is a like a blank or clear canvas for the one to achieve or find it first upon which the the one who find it can re shape the the world in the future in many ways .
One of the way that can happen is by joining all the world or all the races in the one piece world together to upthrow the world government one way of doing tha is by destroying the red line which is a extraordinary task to pull of by one self which could be done by the possible ancient weapon at the raflet which would cause mass destruction due to the destruction of the red line and cause disasters all over the world and there would be no safe place for the people to take shelter and this is where the huge ships like nova like in the fishman island all over the world and shirahoshi commanded by the luffy as they are under his territory and his protection would controle the sea kings in the calm belt to pull or move the mass ships all over the world and this grand fleat of ships would be led by the rasing sunny towards the great sunny new world created by the destruction of the red line.
And due to the mass movements in the sea would cause the destruction of the calm belt and the new world would be of no restrictions to whom so ever in the world and I expect the revolutionarys to lead the people to mass evacuation into the ship's and help to reform a new democratic world government in the newly created world of one piece and the adventure goes on to discover new places in the newly created world and some day when theay all get old and gets retire they pass on theirl will on to the next generation and new erra begins . And the adventure continues with next generation straw hat. I think the final arc may be something like this or something related to this loosely based.