I don't see any other option than keeping everyone on the same worlds that we are on already. We're all high level and have all the best shit (well, some of us), I would think that many new players would prefer to be on a world where there is a lot of other new players, so that they would have an actual low and midgame to play. Mixing new players with players who have every job and craft at 50 is probably not a good idea for at least the first few months. After the new servers have grown and gotten a sustainable economy on their own, us oldbies might be able to switch servers if we want.

Of course, the game shouldn't deny new players access to the old worlds, it should just recommend them to join the new ones.