Had anyone actually seen what race and sex Sheogorath was before the Shivering Isles? In Morrowind, he was a huge stone statue, his most distinguishing features his jacket and cane. It's not like he has to make a personal appearance in every game.
Or he could appear in whatever form he wishes I guess. Daedra can do that, can't they? He'll give you your quests as a swan or a burning bush or a golden shower or something divine like that.
Or maybe someone else has already replaced him offscreen.
Maybe the old Sheogorath has taken his title back.
Maybe Lord Vivec is now Sheogorath?
The third is the fun one: There's no reason whatsoever to assume that the dragon 'V' sound sounds anything at all like the human 'V' sound. There's a number of real-world languages that use (or can use, anyway) the same symbol ("letter") to designate different sounds than the symbol is used to designate in other languages. My own fun idea is that the draconic V is the sound of their upper teeth crunching through the bones of overly curious humans
'Cept that humans can speak Dragonese too. It's a huge plot point, apparently. Some old emperors could do it, as well as the Nord graybeards, whoever
those are. And the PC. The glyph that the devs saw fit to mark with 'V' corresponds to a sound that a human can make. Now, this is just idle speculation, but I think it could be the 'V' sound.