Crack theory:

Paarthurnax, who is now the leader of the dragons (assuming he wasn't killed), invades Cyrodiil and takes over the Empire...and promptly goes to war with the Aldmeri Dominion and wins. Humans and elves are now second class citizens in the eyes of the new dragon ruling class.

There is a new emperor should Mede die: if the player chooses to join the Legion after completing "Hail Sithis!", Tullius' oath still includes swearing to serve the emperor, but excludes Mede's name.

Either that or the new one hasn't been crowned yet which explains why no name was mention in the oath.

That may not necessarily reflect a change in regime; Tullius seems to be first and foremost a man of the Empire (the institution and office,) and only second a man of the Emperor (the individual,) however close the second may be. He's also a soulless (lacking any discernable appreciation for high drama or the romantic,) utilitarian, which can lend itself to being a good leader, and is in the middle of a bitter, bloody war, far from the empire's heartlands, regardless of any potential succession-crisis in Cyrodiil.

In other words, he's a pragmatist hedging his bets.

The big gotcha being "assuming he wasn't killed". For some people he was, thus can't take over the Empire. Besides, Paarth seemed to be the kind to try and avoid taking power, lest his instincts get the better of him again. Even at the end of the MQ, he was off to get dragons to stop being so aggressive, not necessarily to lead them (IIRC).

Odahviing, on the other hand... though he did basically swear fealty to you. I doubt he'd usurp power when he's effectively your pet. Maybe if something happened to you, though.

It should be added that Odahviing doesn't trust Paarthunax. He thinks that power, to replace Alduin as the head-honcho, is exactly what Paarth wants. Even if its under the peaceful teachings of the Way of the Voice.

He also thinks the Way of the Voice is a farce, something for the weak-minded, and that dragons can't truly follow it. Odahviing isn't like Paarthurnax. Odahviing is a dragon through and through, so he doesn't really comprehend things like peace and non-violence like Paarth. He would think Paarth wants power to lead because that would be typical dragon behavior.

Another thing is that Odahviing doesn't really like you. Even after you beat him he doesn't swear loyalty, and he only agrees to do what you say after you beat Alduin and show him that you're the most powerful dragon. He also doesn't like Paarthurnax. IMO, it would fit his character to plant seeds of distrust between you two.

That's why I like him, to be honest. He's a straight shooter. Doesn't patronize me. Knows who's boss. Besides, he isn't named "Ambition Overlord Cruelty". Not that there's anything in a name, I might add.

Or maybe its just that whole "Tsundere" effect that's going to work on me.

I always saw Odahviing as more of a dog, to be honest, though that could just be because his bloody snout was always in my face, and he has dreamy eyes and I just want to cuddle him and-

Ahem.

I'm a little closer to Ki-I mean Fiore on this, I think; his name marks him as a hunter, both cunning and straightforward. Whether the wolf is tamed or biding his time remains to be seen.

Now if you'll forgive me, I'm going to go back and lose myself in those eyes.