It is possible that we could see a mandated maximum seating (or minimum spacing) that would make flying a lot more comfortable than it was.
This would eliminate the tendency to keep downsizing seats to get more people on each plane to be competitive. If all airlines have the same restrictions that behaviour stops.
This would move fares up, but possibly that would just return them to where they were a decade or so back. Not to the outrageous (by today's standards) levels of many decades back.
From the airline's perspective, this also lets them keep more planes busy (which they already own and need to keep busy to pay for) as the passengers per plane go down but revenue per flight stays constant.