I figure, if one person can bring in their love interest, why not the others who's love interests are still alive and well.haha
My opinion (which is just that, my opinion -of course) is that the reason why Pepper makes sense and the others don't is because things with Pepper resolved on a pretty upbeat note in IM2, whereas with everyone else's love interests - it ended on a downer and there's loads of baggage attached to how we last saw them (Banner had to go on the run again, leaving Betty behind....again, Cap was frozen for almost 70 years, Thor and Jane got seperated by the destruction of the Bifrost). There are issues to be resolved with those relationships that don't have to be resolved between Pepper/Stark. As she works closely with him (and as action takes place at Stark tower), her cameo can work without them having to address the romance overly much and having it work.
With the others, if they try to shoehorn them into an already large ensemble cast without addressing the baggage, It would be doing a disservice to the time and development that those relationships deserve.
Like others have said, a mention can be made - Selvig or Coulson giving Thor an update on where she is/that she's safe, and Thor mentioning that he will go see her once Loki is taken care of/secure back in Asgard or whatever. That will work for me.
Like I said, just my opinion, and I hope it made sense.
As for the Japanese trailer?


I totally flipped out at work when I watched it (and I loved, LOVED that they still kept the dialogue in English and just subtitled it for the Japanese). All those new scenes, Hawkeye speaks! The Hellicarrier rising! More Loki! More Thor! GAH!!!! Needs to be May NOW! *lol*