A major risk to airlines in the future will be minimum mandated space per passenger or, if you will, mandated social distancing. The current recommendation in this neck of the woods is 4 square meters per person, which would yield the following maximum capacity for a select few airliners. Please note this does not take into consideration the space needed for galleys and lavatories.
A220-300: 22 pax
A321: 32 pax
787-9: 75 pax
A350-1000: 81 pax
Even if we lower the requirement to 1 or 2 square meters, this will spell the end of commercial aviation as we know it.