It's quite possible they would do nothing. Chase has not reacted to the higher annual fees implemented by American Express Platinum or Citi Prestige. Chase has not introduced a Business version of Sapphire Reserve.
I take what Amex has been doing as of late to the Platinum and now Centurion cards as being a way for Amex to signal to Chase what Chase needs to do to achieve a relatively peaceful duopoly for the two to share and share more profitably: reduce benefits on the Chase Sapphire Reserve and/or hike up the CSR's fee substantially; and also prepare potentially for a new premium card somewhere in between the Platinum and Centurion cards that doesn't out-do Amex because otherwise it could be a costly disruption for Chase and less of a winner for both Amex and Chase.
That Amex has so many of its former employees working for Chase in the UR-earning card area and makes a point of very publicly mentioning that is definitely one way to possibly send a message in a bottle from land to land.