I guess my recollection of the events that went down in the final battle are a little sketchy as (due to my disappointment with the treatment to the Mandarin) I only viewed the movie one time. However, now that you mention it I do recall Killian surviving the exploding suit (guess I tried to block it out), so you may also be correct in assuming that he could survive a missle detonation. So, I guess we will see if he returns. If they do, I just hope that they change the way his extremis powers are portrayed to using more blasts from the hands (in place of his rings I suppose), because that whole breathing fire thing really bugged me. Also, I hope they get him away from the whole business man looking thing, and put him into something that makes him look more like a Warlord. They could even indicate that Trevor's version of the Mandarin was the concept of Killian who he himself has a love for the great conqueror's of the past, as he sees himself as one of them. Also, I would think if he returns it would be most likely in a Masters of Evil / Acts of Vengeance type format, and a more comic book type version of the character would seem to be more in place with the other villians (like Loki, Ultron, Abomination, and others) then a business man looking character. Ultimately if Killian survives, I would like to see him collect his rings from Trevor, Shoot blasts from just his hands (perhaps showing that he now has better control of his powers), and to wear a hood with some style of a robe, gown or perhaps even something else that pays homage to ancient warlords & conquerors. Then perhaps I could see Killian as the real Mandarin from the comics.
Surfer
PS. I know Mandarin has worn suits at times in the comics, but the whole business man thing is so boring & overdone, and it seems like they do that for almost every villain now a days that it does not do anything to identify him as a character. I mean Loki wore a suit for a while, Dr. Doom wore a suit for a while, the suit doesn't help to give the Mandarin his own look that he is really needing. Anyways that all I have to say for now.