Whilst I agree that face to face can never be beaten (I am currently meeting my clients over the phone and Zoom/Skype) we cannot guess that all will return. Not least because, after a major upset - it never does.
Firstly a simple example from another industry: In 1991 I was working in the telecomms consulting world (started in 1977) and had done my fair share of biz travel. The daily rate being paid for contracts collapsed as the recession took hold. It took ten years for the daily rate to get back to what it was - meanwhile inflation had continued.
Secondly: It is not possible to compare the fall out of Covid19 with any previous recession. 2008 had a specific starting point and that was clearly understood. Covid started with, and continues to have, many unknowns. A recession caused by financial means alone is a familiar pattern, I have lived and worked through four of them. But a recession caused by a pandemic is unknown in living memory. Further, the financial skyline had not seen any significant reform after 2008, so all the instabilities of 2008 mostly remain. Then add Covid19 ...
My guess is that the glory days of flying will take a long time to return. If there are fewer Biz pax then prices for leisure will rise and that will flatten demand also amongst main line carriers. Guess by all means - but nobody knows how this will turn out.