Umm.. it's probably an inappropriate question, but I would probably ask them how committed to living in the community was to them. Like... are they happy and foresee themselves looking for new job opportunities, or are they content where they are? Sure, things change... but some people are more commited than others. (For example - I live in a very transient community. I'm a teacher. There are a lot of teachers here who are married to RCMP officers - those teachers will leave after their spouse has done their term up here. Then there are others, who are single and from an area where it's really hard to get teaching work. Those teachers are less likely to look elsewhere and are more likely to commit themselves to living here).

They probably wouldn't tell you anything because "I'm not planning on leaving at the moment", but knowing me I would probably ask anyway!