When 1.3 comes out, there are two options for the current world:
We banish it into the abyss, bringing forth an entirely new world in it’s place. People will be able to pay a cost to have creations imported from the old world.
We keep the current map, but upgrade to 1.3 with it’s new biome code. This will cause a weird cliffy rift to form where old biome generation meets new and new features will only spawn in new areas. This encourages exploration into the distant lands which contain new features.
Not everyone likes change. Fuck the new features. Keep 1.2.4