At the begining there was the first world who was enslaved by the earth god, the enslaved prayed upon the flame/forbidden fruit and Nika answered their prayers.
The earth god was pissed and he alongside the serpent of flame ( red line) fought against Nika and his guys.
The world is destroyed and there is only death and darkness left.
Then a breath, from the void. World 2 restarted anew.
In that world the forest god (probably Imu who inherited the earth gods power) unleashed demons upon the land and Nika(Joyboy) sowed seeds of war.
New fight between the earth god and Nika. The earth god won again.
The third world is ours its yet to come to fruition but it says that the troubled shadow ( Imu imo) will hear the voice of the fragmented moon (Either Garling or BB)
Nika/Luffy will guide the current world order to its end onto a new dawn.
They will meet again imo means the rejoining of the seas through the destruction of the red line/Serpent of Flame.
They can't be met again Nika beat both at the end but the destruction was too severe and he also died at the end of the war.
I dont think Nika beat them lol he either lost or it was a mutual destruction which led to their will going through the ages and Imu then Joyboy and Luffy inheritted their powers.