The only reason Cap and Thor were most likely released in the same year was because "Avengers" is coming out next year. There's only one Marvel movie coming out next year 
The Valkyrie is an odd choice. Other than sharing an Asgardian background, she's never figured all that greatly in Thor's books.( But I'm not up to speed, so that may have changed) The biggest role I recall her having was decades ago when Roy Thomas adapted The Ring of the Nibelung in the Thor comic. Through Odin's manipultions, Thor was tranformed into Siegfried (Seems Don Blake wasn't his first go round as a human) and The Valkyrie is The Valkyrie, Brünnhilde.
You mean only one Marvel Studios/MCU movie. There's also Ghost Rider and Spider-Man.There's only one Marvel movie coming out next year
Asgard has gone through a series of Ragnaroks and rebirths. And, no, Donald Blake was not Thor's first human avatar, though he's probably Thor's last. Matt Fraction's Thor: Ages of Thunder, which deals with the development of Asgard through the Ragnarok cyclces, depicts one of Thor's earlier human incarnations at one point.
I was referring to her appearing in Thor's book(s). I recall that Ultimates storyline. I quit buying the title shortly afterwards. She had an....uh, interesting costume.
^ That doesn't mean they will in the future
According to wikipedia the cast includes:
Thor saw a marginal INCREASE of 1% for the Tuesday dailies. That is important cause big tentpoles more often than not don't increase from Monday to Tuesday.
