Those look like Premium Economy seats based on their generous width, not the crushing 17"-and-change width of typical Economy seats.
I also end up flying a lot of 737s which are 6 across in economy.
Looks like 767s are ~28% of their current fleet's widebodies.
At least Delta provides masks on their red-eye flights.
On 787s, 3-3-3 seems like the standard.
Not sure what Airbus is up to, but I'm guessing they're not selling many planes if their selling point is "higher fuel consumption for every economy passenger!"
Just after refurbishing them for their new business class in priority over other aircraft?
1) they would shift the time of departure from 6p - midnight to 3 am. They'd let everyone sleep in a special part of the gate area which would close to passengers not on the flight. Passengers could also go on board the plane and sleep while it is at the gate if they preferred. About 30 minutes before departure everyone would be awakened and they would board. This would avoid having to arrive 2 hours ahead of time and the delayed departure would still get the passengers to their destination at a reasonable time.
OR
2) they would get rid of the overhead section of the plane for redeye flights. They would stack horizontal chairs three high and everyone would be horizontal for the entire flight.
Real estate (as in space) on a plane is probably the most expensive in the world. While airlines reserve space for (for example) a bar in business class (and to the best of my knowledge only in the A380) a gym would use too much space.
There's also the issue with turbulence to consider, which would make a gym (at least without significant adaptions to the machines) rather impractical.
Offering a cheap (or at least significantly cheaper) option to lie flat would eat into their own revenue.
Few people can manage that