Despite 1.6.4 saving structure data in the world to prepare for 1.7, Witch Huts don't seem to be included.

When I loaded up a world with a witch hut in it in 1.6.4, there was no witchhut.dat when I looked inside the save folder. I saw Mineshaft.dat, Village.dat and Stronghold.dat, but no Witchhut.dat. I expected to see the Witch Hut saved in the data.

How to reproduce:
Start a new world with the seed '2' (Yes, just the number 2). There is a witch hut at x: 3 z:160. Close Minecraft.
Then go into your Minecraft saves folder at %appdata%/.minecraft/saves. Click on the world you just created, then click on the 'data' folder. Inside you should find names of structures, but no witch hut file.