I spoke with a very Senior United capt (30 years) last week. He said he gave up long ago trying to predict this industry.
I think we are on a slow and steady upward trajectory that may flatten out a few times before we are back to "normal". The only thing I see that may stall the increase in demand is a reluctance of people to get vaccinated. My guess is many central and south american countries, all of Asia and Europe will eventually require travellers to be vaccinated or show a certificate of recovery to travel.
My crystal ball!