Do natural structures generate above 128 blocks?

Solution 1:

Dinnerbone has answered this question on reddit:

Will the terrain generator ever be updated to use the full 256 blocks of build height?

It's intentionally designed to only go as high as it does right now. Maybe in the future, or with different generators/options, but right now we're happy with the extra breathing room for players.

Solution 2:

No, natural structures will not generate any differently as part of the height limit change. This change is thanks to the conversion to the new file format, Anvil, which supports layers 0-255 (as opposed to the Region file format, which only supports layers 0-127). The terrain generator works just like it used to, and blocks between layers 128-255 just default to air.

Solution 3:

It doesn't generate terrain above 128 just like the old terrain generation everthing above there is just air, but if you want there's a mod that changes this, all it does is change a few numbers in the terrain generation code the rest stays the same, I'm pretty sure its called Dynamic Heights Mod (or something along those lines).