if i have world seed of 1.6.4 ( and some map already generate on that seed ) and get up to 1.7.2 the world will have new biome , new layout of 1.7.2 or i need some seed of 1.7.2 to have new biome on the world ?
stutiguias Once you update to 1.7, the unloaded chunks on your server will generate as 1.7, there's nothing you need to do.
stutiguias There may be some nasty transitions though in your world. There are tools out there that can fix that; just a heads up.
My map has some transitions like that from previous updates. Stuff like the ocean leading into a ravine, and huge sheer cliffs. They players seem to like them. They blame them on Herobrine.