We dont need to see aliens though, just say Mandarin forged the rings from alien technology, it doesnt really have to be explained other than it was a crashed UFO.
They could just have it that rings were designed from alien technology found in a crashed UFO, IMO that would be acceptable without being TOO beyond the realms of possibilty for realistic sci-fi.
Correct me if I'm wrong, but in the new MARVEL ADVENTURES IRON MAN comics, they introduced Mandarin's rings as though he made them himself. (I'll have to go back and check) and in the regular 616 world, they're getting away from the Fu Manchu look and making Mandy a suave businessman type.
Favs said to pay close attention to the comics when he was talking about Mandy, I'm betting they're going to combine the two versions for the Mandarin in the movie.
I've always wondered if they could still get away with that in a film, but I'm not sure if they could. Considering how grounded in reality the first film seems to be, it would seem weird if in the sequel they alluded to alien technology.