In Deathly Hallows, we see that
Tonks and Remus
die. After this:
Would Lupin transform into a werewolf during the next full moon? Would Tonks’s face and body revert to its natural state, because she no longer has any conscious control?
The last one seems more likely, but thoughts anyone?
I don't think that this is directly addressed in the books, but if it helps, the closest phenomena we see is, I think, Barty Crouch's mother. Being under the effect of a polyjuice potion, she died, and her body didn't revert to its original form.
So we get that this magical concoction doesn't seem to work on dead bodies. Why? Well, that's not explicitly explained either, but I feel it is pretty logical: the only reaction a corpse can have is rotting.
