Depends on your area I guess. In North-Eastern Asia my experience is that 'expats' refers to those who have moved for good, and anyone staying temporarily is just a 'foreigner'.
My dongbei experience has it that all foreigners are referred to as expats if they are working for a real company and not just teaching English...but expat is actually a technical term that our HR uses to distinguish between packaged employees (many of whom are Chinese with green cards or us citizenship) and random locally hired foreigners (who have no packages and are more likely not Chinese).