I have flown UAL, DAL, and AAL and I have noticed that my mobile boarding pass updates with the current gate information on a regular basis.
I am requesting SWA implement this feature with their mobile boarding passes. If I load my mobile boarding pass into my wallet at 24-hours prior to departure, understandably it will not have the departure gate information. However when I arrive at the airport a few minutes to a few hours before my flight, I should be able to see the current departure gate for my flight on the mobile boarding pass.
In addition I have noticed on the AAL mobile boarding pass that there is a yellow circle around the gate information (or any other changed information such as departure time) that has changed. It is a very handy and convenient feature.