American Airlines (Dallas/Fort Worth) introduced the new two-class Airbus A321-200 on the Los Angeles-Miami route on August 1 (rather than Los Angeles-Dallas/Fort Worth route) according to Airline Route.
Other planned Airbus A321 routes:
Los Angeles-Dallas/Fort Worth (August 22)
Los Angeles-Las Vegas (September 3)
Miami-Las Vegas (September 3)
Dallas/Fort Worth-San Francisco (September 3)
Dallas/Fort Worth-Miami (October 2)
Dallas/Fort Worth-Orlando (October 2)
Miami-Orlando (October 2)
Copyright Photo: Michael B. Ing/AirlinersGallery.com. Airbus A321-231 N101NN (msn 5834) prepares to land at Los Angeles International Airport.
American Airlines (current livery): 
I think the way American is utilizing the A321 is good but I think two A319s should run the MCO-MIA flights instead of 1 A321. The US Airways 319s could do well on this route. What do you think?
I believe they want to showcase this new type on this important connecting route for Latin visitors.
All the best.
Bruce