It looks like Thor could be trading girlfriends in the upcoming sequel. Natalie Portman looks unlikely to return so it appears that love interest duties could fall to Jamie Alexander who plays Sif. It makes more sense that Thor would be attracted to his fellow God than a generic scientist who seemed to be there simply to appeal to non-comic books. Thor and Sif have history in the comics too so it makes more sense from whatever way you look at it. It’s certainly a direction that Jamie Alexander wants to go in.
“I’m a comic book nerd at heart, so I’d like to see the relationship between Thor and Sif progress,” said Alexander to MTV. “Whether or not they do that, we’re not sure yet. We’ll see. I think that element will be in there, but I don’t know how much.”