FWIW, I think that Southwest will continue to use this gate in terminal A throughout the day as demand warrants. From my general observations, there was an airport-wide gate shakeup a little over a month ago. Delta no longer utlizes gate 8, which has moved to house most United flights. Alaska operates a good amount out of gate 18 now, and I think Air Canada moved from 1 to 3.
As we all know, the airport is squeezed for gates. The airport authority may have demanded Southwest operate out of terminal A to balance the gate burden felt by Alaska, who has a pretty crummy gate arrangement at SJC IMHO. Southwest always seemed to have the the best setup of the airlines in terms of being located in the nice terminal B with consolidated operations at gates 19-26. Certainly warranted, considering WN is the largest carrier here by a mile.
Things seem to be in flux at SJC with rapid growth, etc, so it's definitely interesting to observe how the different airlines and airport make the best of a tight gate squeeze.