I've heard that they're waiting for 1.7 to be released so that they can load the new world in the 1.7 world generation with all the new biomes and other things. I'm not sure when the offical 1.7 release is, but it's not going to be for a while. Apart from this, most of the survival community has requested a "restart" in which everything has been resetted like money, terrain generation, and items/ender chests to give everyone a fresh new start. The survival server, as far as I know, will not be online anytime soon, so for now, we just have to wait