Spoilers for Doctor Strange here, so turn back if you haven't caught the film yet.
So Kaecilius doesn't end up having a great time at the end of Doctor Strange. He gets bannished from the realm of earth by Dormammu in a bargain with Strange looking pretty shrivled, burned and all that.
But what are the prospects of him coming back to the MCU? Speaking CinemaBlend, actor Mads Mikkelsen seemed to downplay it, saying:
I don't know. He was not looking too sharp in the end of this movie, but you never know.
When reminded he didn't die, but rather was violently and terribly banished to another reality, he said:
Yeah, it's like [snaps] a blink of an eye away.
I thought Mikkelsen was a good addition to the MCU rogues gallery, but I'm not going to hold my breath in seeing him again. However, if it did happen, I'd be well up for it.