I don't think it'll be ignored forever. If they didn't want to save a reunion for a movie, they would have let Lady Sif tell Thor. That being said, it seems less necessary than I would have once imagined.
As for the general movie-going audience's expectations, I would imagine they have some idea that he's not dead because he keeps appearing in ads for a Marvel television show. They probably don't know the details, but I don't think they need to know them.