It appears WGA will be treated like Basic with regards to fund expiration:
From Southwest email reply->Reddit: If you booked a Wanna Get Away (now Basic fare) reservation 6 months or more prior to your travel date and subsequently decide to cancel, unfortunately, you will not be eligible for a flight credit. This is due to the fact that any flight credit associated with your Basic fare reservation expires 6 months from the date of purchase.
This is unclear. If you booked before May 28, the expiration clock starts when you cancel post May 27. WGA fare rules apply unless you actually booked Basic. Basic can't be booked until May 28. Unless I misunderstood something.