mh... okaaay... it will be ONLY available in germany because its released by "Concorde Home Entertainment". Maybe it will be available at Amazon.de too... we have to wait.
I wouldn't think of these as a trilogy either, especially since the third ties in with the avengers so closely.
But then again, concorde have already released steels for them individually, and as a 1 & 2 set.
They might as well go the whole hog with having 5 steelbooks for three films.