Sure will be interesting to see what they do to American's A321 that will have 102 seats in a three class configuration.
This configuration is only slated for JFK-SFO and JFK-LAX. I believe AA will have a more standard A321 configuration for A321s used on other routes.
That said, I'll be surprised if AA+US keeps a dedicated A321 fleet with this few seats for the JFK-SFO and JFK-LAX runs. Although, UA does, so maybe AA+US will too.