Marvel will be releasing the new trailer for Thor: The Dark World on Wednesday, August 7th! It will be a part of YouTube's "Geek Week" programing event taking place from August 4th to the 10th.
I imagine the trailer will contain a lot of footage that was screened this last weekend during Comic-Con, which was pretty spectacular. The last thing they showed from the footage had everyone in shock. I won't tell you what it is because it's definitely spoiler material.
But the trailer comes out soon, so you just have to be patient.