Mouth of Sauron as Lord of Isengard

[Alcuin]

I’m reading LotR again, and I have a question:

Supposing Frodo, Sam, and Gollum (let’s not forget him!) failed together to destroy the One Ring…

Had Sauron gotten his way at the Morannon, and the West accepted the demands of Sauron delivered by the Mouth of Sauron…

Do you suppose Sauron would have given his servant, Mouth of Sauron, the Ring of the deposed Witch-king?

And what do you suppose became of that old fellow, the Witch-king? I think his spirit was unable to leave the Circles of the World, bound to his Ring until either Sauron broke the binding, which he might not be able to easily accomplish without the One, though I suppose he could do it in time: he had after all been rather preoccupied during the ten day between the old boy’s discomfiture at the Battle of the Pelennor Fields and the Army of Gondor’s arrival at the Morannon, or the One Ring was destroyed, leaving the soul of the poor old Witch-king rather weak and – pardon the expression – dispirited before the throne of his no doubt unforgiving master, Sauron.