I think some folks might be of the opinion that Mordenkainen was not given much reverence in that he was defeated by Strahd. I personally don't mind, but I've seen that sentiment expressed online.
My game will be returning to Barovia at some point, probably for a visit to the Amber Temple. I had modified the adventure quite a bit to fit my campaign; the way I had it was that the Tome of Strahd was kind of like a physical manifestation of his agreement with the Dark Powers. So it could be used by others to break Strahd's conmection to the Dark Powersand to establish their own connection.
So at the end, shortly after my PCs killed Strahd, the mists parted and the sun shone upon Barovia, and the Abbott floated down to assure my PCs that as the mew Lord of Barovia, he would ensure the safety of the people there.
So an insane fallen angel is now in charge...so I expect things will go sour pretty quickly.