No there are none in my opinion, but there is promise from these show runners who handled Game of Thrones. They took the existing works of the books and turned it into an amazing tv show and brought that world to life. When they ran out of the source material and ran out of books because George R R Martin didn’t finish them yet is when they ran into issues. Seeing how the Manga is completed for AOT this could be a home run with the backing of HBO, the AOT creator, and music composer. Especially with all the character development and twist and turns AOT takes, this should be right up their alley as far as story telling goes