Could you tell me where you got this info?
Simple observation and in-game dialogue, the empire holds more holds then Ulfric and even the people inside Stormcloak territory don't show any interest towards the stormcloaks save for Windhelm which seems to be the place with the most stormcloak support.
It depends on which side of the civil war is considered canon. If the Empire wins, I don't think they'll die off. General Tullius may not be one for Nordic culture, but he comes across as a very astute fellow and I can...
Spoiler See him potentially filling the void after Titus Mede II was assassinated
If the Stormcloaks win, then I can see High Rock rolling the dice and going for independence too.
If you join the imperial side of the civil war then Tulius will admit that he may have been a tad ignorant and plans to change this by having Rikke teach him about nord culture and custom while Ulfric just shows signs of being oppressive and forceful to get his way towards the Jarls, qualities of a Tyrant also High Rock loves the empire, always had and I highly doubt they'd fight along side Ulfric.
The bloodline that made the Empire great is dead. The Empire we know now is alive, but no longer represents the people of Tamriel. Ulfric at least represents Skyrim.
People seem to think that Tullius is in charge of the Empire, when in fact he could be dropped like an argonian maids dress in a heart beat if it meant benefiting the Emperor and his goals.
For the time being Ulfric is the lesser of evils, there may be a time when he is not, however as of now I think he is the right decision.
If you actually read a lot of the lore surrounding the septim dynasty you'll find that they really aren't that great, they've had several incidents and have shown numerous amounts of weakness, hell even Tiber Septim seems like a dike if you read most of his lore. Also Your claim that Medes II only uses people to further his own desires, this is literally nothing but a biased opinion :\ we see no evidence of him being like that.
But Ulfric is far from the right decision, he is a horrible leader, a coward, a traitor and a tyrant. He will not be able to fight the Dominion off as much as a unified empire.
I sometimes wonder if Imperial players notice how black and white "the empire is the only thing that can defeat the Thalmor" sounds. That seems pretty uncharacteristic of Bethesda.
No, not really the Empire has always been glorified in Bethesda games, dating back to the first and second empires. The third empire wasn't the only one that was powerful or strong and the fourth empire is very strong. I believe as a unified empire it can restore Tamriel to a somewhat peaceful continent unlike a divided one which would happen if every province turned independent which would just lead to more wars and unworthy claims to land or wars to conquer each other.