According to this thread on FlyerTalk, Southwest Rapid Rewards is offering a fast track to A-List membership after 5 roundtrips or 10 oneways between 4/2 and 6/15. The offer is apparently targeted so it may not show up in your available promotions list. But it’s worth signing into your Rapid Rewards account to see if it’s there.
Apparently not targeted afterall. Go here and register.