So far everything I have killed their corpse has not vanished. I have traveled the roads and seen animals I have killed in the past but for some reason ALL my dragon kills are gone. I thought the dragon skeletons were suppose to never vanish? I really miss the dragon skeleton I killed

It's part of making space for the game I guess.
Automatic disposing of the bodies, helps memory.
But don't quote me, that's my opinion.

It might be a bug with the coordinates. Yesterday I left whiterun and saw a dragon skeleton falling off the city walls, as if it had been picked up and dropped. So maybe yours have just teleported somewhere else? Let us know if you run into any of them later.

I've gone back to dragon bodies to get my hides and bones (as they are so damn heavy), the skeleton was in the floor with the head sticking out xD

Seems I'm not the only one with the problem then. I got annoyed because I can go into a building and come out and if a dragon skeleton was there it is no longer. It only happens with the cool dragon skeletons, there are dead dogs and giants/mammoths all over the place and they never disappear.

An example is I just killed a dragon near the stables at Windhelm and went into the stable house and came back out and the dragon remains were gone. Maybe I should leave some loot on the remains to see if the skeletons won't vanish?