I don't doubt everyone is serious, but there were so many people this summer who were saying they would never go back to WDW if masks are required there. Yet, most WDW parks are booked solid months out, and people can't find hotel availability six months from now.
It doesn't always seem this way on discussion boards where anti-maskers tend to be very vocal, but polls show the majority of American adults still support mask mandates. This support might change as more children are eligible to be vaccinated. For now though, Disney would lose the support of more people by ending their mask requirements than by keeping them.
Personally, I don't see a mask requirements changing until children 2+ can be vaccinated in the late summer or early fall, especially if Disney wants to reduce social distancing from 6 feet to 3 feet. I think they are more likely to change social distancing requirements because it allows them to fit more people into queues and rides (and ultimately the park). Changing social distancing will mean more revenue for Disney. Removing the mask requirement would not mean more revenue for Disney. So, I think social distancing will be what changes this summer, and not the mask requirement.
If I were to take a wild stab in the dark regarding the timing of various changes at Disney World, this is what I would guess:
July 1 - Social distancing officially reduced and park capacity increased (College Program castmembers should be trained by this date, and it will allow Disney to open the parks up more for 4th of July).
October 1 - Outdoor mask requirement lifted in response to all children 2+ being eligible for vaccination.
(Edit to add: Part of me thinks Disney would still require masks in the queues, though, since people in line might stand next to the same people for 30 minutes to an hour at a time. Perhaps there will be cast members standing at the entrances of queues and buildings, asking people to put on masks, similar to how they would be at the entrances of queues for FastPass).
February 1 - Indoor mask requirement lifted (I chose this date because it's after the major holidays. I don't think they could do January 1 because the parks are so crowded for New Year's and winter break).
Of course, I could be wrong! That's just my perspective, thoughts, and guesses.