I have to debunk their theory on Namor. A spot smack-dab in the middle of the Atlantic Ocean? Could be where Thor's base of operations is (you'll need to read The Ultimates to understand this). Obviously, two locations for Thor would be redundant, but if you (again) read The Ultimates, you'd get where I'm coming from.
I also don't know why there'd be a circle concentrating on Germany, as Red Skull is a villain and not a hero. As far as I can tell about that site, they're mostly theorizing on who the members of The Avengers would be, so adding a villain into that list is whack. I can't think of anyone who comes from that region that would be a hero, so hmmm...
I like their line on thinking on including Black Panther, though, for all the reasons they listed (Cap's shield being made of the vibranium, and also that T'Challa was a temporary member of The Avengers).
It's safe to assume we already know who all the members of The Avengers in the film will be because of the previously established characters and upcoming films. The Hulk and Iron Man already have been established, and Thor, Captain America, and Ant Man & The Wasp have films coming up. To me, that shows a roster set in stone. I wouldn't be against Black Panther being in The Avengers because I think he's badass, but it doesn't make sense to have him highlighted. Red Skull, either.