I mean, I haven't even seen announcements to the effect of "fees are coming back, but we're temporarily extending the period where we don't have them". The broader public has always hated the fees and felt them unfair....but *doesn't* hate the idea of basic economy. So my guess is that they're keep the marketing benefits of having no change fees on "standard" economy fares, like Southwest has, knowing full well they can throttle the basic economy and standard fares however they like - with little to no PR backlash.

In other words, any claim by the airlines to have "lost" revenue from change fees would have to take into account the benefit they've gained by allowing people to make more speculative bookings, and then hold credit they may or may not use if they cancel their flights later. They've probably won back some WN fliers who preferred the legacy carriers but don't always have ironclad travel plans and couldn't previously book legacies because of the fees.