My personal opinion is that this summer is going to be another bust for the airlines. Even with the vaccine distribution being given high priority it is still going to move slowly, and travel restrictions will be lifted even slower. The new administration seems as though they will be unapologetic about attempting to control the virus even if it's at the expense of the airline industry.
My expectation right now is that most folks will probably be recalled around this time next year in anticipation of the 2022 spring break/summer travel season. Of course that will vary somewhat airline by airline, just as the furloughs themselves have varied. Management will definitely be looking for ways to dig out of the massive debt 2019 incurred, and keeping labor costs low will be one of the top ways to do it. Also each airline has a unique business model, and since the recovery hasn't really even started yet it's still unknown to what extent each type of revenue (Intl, domestic, business, leisure) will come back in the short term. Customer habits may change on the other side of this whether due to economic necessity (some people can't afford to travel anymore) or preference (some people prefer meeting virtually.)
I am as eager as anyone to get my job back, but unfortunately I don't think we've turned the corner on this thing yet. To address OP's question, I wouldn't expect a new hire class at any majors until maybe early 2023 at best. I think after 9/11 my airline didn't hire anyone for about 5 years.