You got your wish. One flight out of the 8 daily flights each way has been changed to an MD88 aircraft...142 seats. I followed the bookings for about two weeks and noticed that with the exception of Fridays to PC and Sundays out of PC the aircraft is less than half full which means that if bookings don't increase it will revert back to the ASA aircraft, or they will drop the flight outright. During that same period all the ASA aircraft are 60% ish full, too. That's not economical use of a resource.
Looked at the same period into VPS. During that time, VPS still spanks PC. Admittedly, these booking were made a good while ago. I'll check again in a couple weeks to see if I can get a trend one way or another.
You have to keep in mind that there's no incentive for Delta to offer larger aircraft just because of SW's service. SW is in bed with St. Joe who has agreed to offset all of their losses on flights into and out of PC for the next three years.