This was briefly touched on in an earlier GQ thread. In English (American English, anyway), “bye” and “see ya” are just general valedictory phrases (and there are lots more). “Good-bye” can be, but, depending on how it’s said, can imply a permanent departure (and there are probably others, too). “Farewell” probably implies permanence, but I don’t think I’ve ever heard anyone use it.
In other languares, are there similar phrases a distinction of permanent vs. non-permanent departures?