The Season 3 finale of The Flash will serve as the definitive conclusion of the current story arc, and it will introduce an entirely new one that the series will expand upon next year.
Specifics about how this will all play out remain shaky at best, but the report seems to make it clear that the overarching problems that Barry will have to deal with during the events of The Flash’s fourth season will begin to make themselves apparent in the final moments of Season 3.
TVLine’s report states that despite dealing with a giant setback, Team Flash will manage to take down Savitar (or make him less of a threat, at the very least), but that victory will come at an unexpected cost.