Nobody says the "New World" part of the story needs to last very long; I can't imagine there to be too much out there.
Correct me if I'm wrong, but didn't Crocus said you need to go through 4 or 7 islands before reaching the mid-way point? I dunno, I think he specified a number…
Whiskey Peak (1)
Drum Island (2)
Alabasta (3)
Mock Town (4)
Skypiea (5)
Longring Longland (6)
Water Seven (7)
Lord, Oda isn't going to finish this. He'll be writing from beyond the grave.