SOS on that team is up near the 300 range, meaning they had about the easiest schedule of any tournament team. It won't matter, most sources say Winthrop is a 13 or 14 seed, which means no chance they fall to 16.
I would say in the next 20 years, the chances of a 16 winning are maybe 10-15% at best. It just won't happen barring some major changes in the game such as an NBA minor league that picks up most of the top talent out of HS. Short of that, it just isn't likely to happen.