Yeah, over time, using the dark side may has disfigured his face, but it his still his true face. How old is he???
The face of Palpatine the senator was just a cover up....I think.
I don't really know
But I do think we're seeing Palpatine revert to his true form. A few points to consider:
* The "deformed" excuse is his cover when he addresses the senate, which is clever as it has the added side-effects of generating sympathy for him and hatred toward the Jedi. I don't think that was there as an explanation for the viewers.
* If Palpatine's appearance were truly the result of being injured, why on earth is it symmetrical? His head and features are totally symmetrical from what I can see. That's not an injury.
* Throughout the first and second movies, there is repeated mention that the dark side clouds the vision of the Jedi. I believe that Palpatine has harnessed some dark side power that allows him to project a false image of himself and hide in plain sight. The Jedi can sense it (a phantom menace) but they can't figure out what it is.
* During his fight with Windu (which I believe Sidious doesn't forfeit on purpose), he is becoming fatigued and drained and that ability to maintain the facade goes away.
* The change in the appearance of his eyes are a result of injury?
* The prequels have this consistent mirror image/duality thing going on. Characters are not always what they seem. Think of Padme and her double in the first and second films. Being deformed and injured doesn't play into that duality theme; having two distinct appearances does.