Its possible that the Mandarin, wearing the rings, could be in control of Fin Fang Foom. Which looks to be depicted in the background here...
Maybe we'll see FFF, maybe not.
Im just saying that it could make sense and give the rings purpose. Regardless of actually seeing FFF in action or not. What do you think? Has there been any speculation on a possible appearance of FFF? Maybe a post credit scene FFF is awoken!?!