If it's been pointed out to you before that your spelling needs improvement, and you still haven't improved, thats kinda rude. I'm not asking for you to be Marriam-Webster here, but just give your posts a quick read through before clicking the "Add Reply" button, k?
Anyway, i have several refutes for your argument:
1) Falmer have been generally unseen for several hundred years, so that means they either don't exist or exist in such small numbers that they wouldn't be able to have any impact on Tamriel. As such, if a population of Falmer were to be found living in Skyrim, they would likely be met by resistant from the Mer-hating Nords, who would likely bear a grudge against them for the past, and therefore would not survive long
2) Just because the Empire may or may not fall does not mean that Imperials will all dissapear. They may decide to rename themselves to reflect their new status in the world, or they may retain it as a way to remind themselves of the past, but they won't just die off. And about them being absorbed by the other human cultures, i doubt an entire civilization could be dissolved in a matter of years just because they don't have a genetic leader right now. Besides, the Empire might not even fall
3) Even if the Empire did fall, and if the Emperial's were wiped out in some kind of mass genoside, theres no law stating they need to be replaced by a new race. And as far as the smart warrior you mentioned, Redguards could do it.