Could it be a bit of foreshadowing or just a really cool item? For the Blizzcon 2011 sale this year, one of the new items is a set of movie style posters based on the Opera event from Karazhan. The link goes to wow insider because the items aren't viewable by everyone yet (only if you have a physical Blizzcon ticket. Which I don't because Blizzards RNG hates me and I have never been able to buy one).
I for one would love to see either a heroic version or Kara extended. Kara is my favorite raid and I think it is probably the best they have done in terms of raid design.