Chase could raise the AF for *new* accounts while grandfathering the old AF for longstanding cardholders. Why? That would dissuade cancelling the card and reapplying when the 48-month bonus-moratorium ends in August 2020.
RNE, musing.
Won't happen, at least not long-term. There may be a transition period for existing card holders, but why would they lock them in at $450? I'd be willing to be that those who would drop the card over a $100 increase probably aren't Chase's bread and butter anyways.