Yes and no. There has not been a change fee, but you had to pay a fare difference. As long as it is similar travel dates and the same airport to airport, though, I am pretty sure you don't even have to pay that right now. At least that is how I am reading it.
If your flight is cancelled SWA will automatically assign another one same day, then send you an email
I was hoping mine would get cancelled end of June. Thrilled to jump on earlier one I wanted that I’ve been stalking, but always hundreds more than I was prepared to pay.
FYI it did show sold out for nearly a week before the cancellation, might be a early sign.
Copy for the cancellation/rescheduling email for reference:
We want to make you aware of a change we’ve made to your upcoming trip. This was done proactively due to a Southwest flight schedule change on your day of travel.
Please review your new itinerary below.
Your reservation is confirmed and no further action is required.
In the event this new itinerary does not work for you, we are offering the one time opportunity to change your flight date(s) and/or time(s) by up to 14 days from original travel date at no additional cost in accordance with our established reaccommodation practices.
For expedited service, you can change your flight at
www.southwest.com/rebook3 between the hours of 12:00pm (CDT) April 14, 2019 and 11:59pm (CDT) April 19, 2019. Should you need further assistance, you can reach a Southwest Representative at
888-871-8321. Please keep in mind that the time to reach a representative may be longer than normal during this time.
We look forward to seeing you onboard soon.
-Your friends at Southwest