Since technically, the Empire's throne is supposed to be held by someone that is dragonborn, shouldn't there be some political movement afoot to replace Titus Meade II with the one and only person proven to be dragonborn (complete with the Greybeards' Stamp of Approval)? This could get real interesting when the Powers That Be in Cyrodiil perceive the main character to be a potential threat to the status quo. [First they would deny his veracity. Then after he proves his bona fides, they would try to recruit him to be just a member of the Emperor's court. Then if the character refuses or becomes too popular, he would become a threat that would need to be eliminated.]

I can see that there would be a HUGE appeal to the citizens to have a "legitimate" dragonborn on the throne. (Even if that candidate isn't human.) By putting him there, it would miraculously reenergize the Empire and make it possible to go kick those uppity Thalmor back to the Summerset Isle where they belong! [AND wash the dishes and babysit the kids and everything else you could ever want from a dragonborn! Batteries not included.]

I'd be willing to bet good money that when TES VI is finally released (after Fallout 4 has it's turn) we'll find out that

Now, where all that leaves Tamriel and the empire is anyones guess, but I'd make another guess that we will never personally see the Thalmor again. Might hear about them in future games...most likely in the past tense. They were a decent enemy in Skyrim, but TBH I don't think they warrant another game revolving around them. Even though the game wasn't solely focused on them, once was quite enough. No need to bring them back for more.

EDIT: After re reading the opening post, it could potentially wind up being that the LDB is Tamriel's Julius Caesar. But again, his/her identity will be lost and largely forgotten by the time of TESVI.