Originally Posted by American Maid
I think the exact characterization was "Thor becomes reunited with Jane who becomes possessed by a Dark Spirit, which is connected with the Dark Elves"
So not necessarily a Dark Elf him/herself, but affiliated with them.
Also, the general thinking is that the spoilers concern things that happen early in the film. So if these scenes with Malekith and/or Jane (haven't seen them all together yet) are set early in the film, then I agree it's quite possible. If these scenes are set late in the film, maybe less likely.
I would think what they are filming now is early on which explains why Loki isn't involved and why it is a more open set. No way to know it for sure but it's an awfully big coincidence that Malekith is on Earth where we know Jane is so they very well could cross paths.
I also think whatever they filmed in Iceland (?) is the finale which is why there are no pictures of it. lol