You know, she went to college at the end of her last run. So it would be logical for her to return, maybe. She was also created under Dena Higley (incoming co-head writer)'s tenure.
That being said, I don't think there's any reason she WOULD come back to Salem. (Does she have family there? Friends beyond Chad/Will still around? etc.) Also it seems like we're looking at a Ben/Abby/Chad triangle, and I'm not sure they're looking to invest in such a small character (she was on the show for about 18 months) when they have so many vets coming back. Of course, the current writers are portraying Abby/Chad as the new "golden" couple, and that could change when Higley and Josh Griffith take charge.
Personally, I never cared much for Mia, but didn't despise her either.