Well considering only mention about black dragons is from Akavir and the Skyrim cover does say talk about dragons with black scales we're on the right tracks.
And then if the cat folk of Akavir are trying to become dragons and they clearly can become dragons - and they want to invade Tamriel I think this is pretty straight forward.
The lore what we currently have to work on doesn't of course bring us the full picture. Bethesda is of course coming up with it as they go along.
I am not a lore master, by a long shot. I just know that it's made by developers of a game. They can twist anything so that it suits their purpose, they decide what happens in the future of this universe.
People wanted dragons, they've been wanted in the game from since Morrowind. Now what if Bethesda wanted us to fight against the biggest and the baddest dragon of them all.
The entire article is pretty much sourced off Mysterious Akavir. Again, if you know better, and you have sources, there is edit button.
Dude, don't argue. Anyone who knows anything will tell you that The Imperial Library is where the "good" and "real" lore is. I used to go to UESP just like you but thats really just good for gameplay. It is very very good for gameplay.