I have been messing around in the new Minecraft snapshot. I'm not entirely sure if the developers are already aware of this or not, but when I walked into the Nether to see if any generation has been unintentionally changed, there appears to have been. None of the Nether biomes (besides the Basalt Delta) has actually generated in the Nether. The Nether Fortresses and the Bastions are left untouched, but the Nether biomes have sort of been wiped away, the only things that exist withing the biomes are the twisting vines and weeping vines. (and of course the basalt pillars for the soulsand valley)