b) Their WFH staff are more productive than their office staff.
This probably varies place to place, person to person. However, over the course of, say, 10 years, productivity would likely drop in a 100% WFH scenario. People retire and the new hires never really find their groove without the in person experience.
Just let those leases expire when they do
Some of these leases are absurdly long, like decades long. Some own the buildings rather than lease, so they’d need to sell, but who would be buying?
I do see significant reduction in office space and more aggressive ‘hot desking’ to size a lower occupancy rate due to increased WFH. Before pandemic, our office planned to 80% occupancy, based on measuring generally 60% occupancy (between sick days, vacations, meetings, and travel, a lot of people aren’t at their desks). I would not be surprised for them to size for, say, 50% occupancy if opportunities to exit lease for some of the buildings comes up.