Since the whole cast aged 15 years, then you start with a 15 year gap in Enterprises' history. Maybe the series is one single arc, ending with the formal formation of the Federation (since we know that happens anyway). The arc is the journey the Alpha Quadrant takes to get to that event.
This would be the most likely scenario. They're not going to pick up where they left off 15 years ago, and they're not going to reboot the show. But none of this is going to happen anyway, because there aren't any stories a 15-year-later sequel to ENT would cover that SNW couldn't cover.