I keep having to remind you that just because it may be based on some elements and characters doesn't mean it'll be followed exactly, my friend.

Feige knows how popular Loki is and he would be a fool to not use him significantly, but they do need to use him differently than has been before, otherwise people will get bored with the same fights over and over.
Was the story of the Destroyer's demise exactly what it was in comics? Was how Thor met Jane exactly as it was in comics? Was anything in Avengers, other than the villain who brought them together, exactly as it was in the comics? No. No. And no. Because they are telling a brand new story!!! If they were just identically rehashing a story that they already told in the comics, there would certainly be no need to keep so many secrets in that case. Just tell people to read the comics and they'll know what they'll be seeing in a year.
No, I have a whole year to wait and my hopes will remain up regarding Loki's part in it until the day I go into the theater. Ain't nobody gonna bring me down.

t: If I get disappointed, so what? *shrugs* it wouldn't be the first time. And I'm a big girl, I can handle it.

lol...
Here is a quote from end of April by the way, probably prior to him reading a script but I suspect the actors have a general idea at that point what the story arcs will be heading towards...
Its probably time (for another villain). Im most excited about really taking the relationship between Loki and Thor to another level. Because obviously the action of Thor 2 will have to begin where Avengers leaves off and what interests me and I think Chris too is whats Odin going to say about all of this and about what happened in Avengers and can Odin and Thor find forgiveness for Loki in their own hearts and Loki accept that forgiveness, can he forgive himself? What will it take to bring Loki back from the brink of the dark side. And then Thor has to deal with everything thats happened up at Asgard during his absence! ~ Tom Hiddleston April 2012
http://collider.com/tom-hiddleston-thor-2-sequel-the-avengers-interview/160736/
Feige:Were going to see the other side of Asgard. Its not all polished and golden in this film.
And the events of Avengers will have affected Thor for sure. His relationship with Loki will continue to evolve, and the biggest part is Natalie and Thor returning with Jane Foster.
"Evolve" meaning not stay the same. Change... and that requires at least some screen time to explain, doesn't it?
and again this one...
Im assuming youve figured out the villain. Is Loki a big part, is he a minor part?
Feige: Loki has a part, but there will be a different villain, another big villain. But you cant do a Thor movie without Loki.
So, Feige being asked specifically if Loki has a big part or a minor part and Feige simply says he has a "part". So I'd say based on that the truth is somewhere in between.

And he almost seems to no longer be categorizing Loki as a villain here, which is interesting...