I don't WFH, it isn't possible in my job so I have no skin in the game either way but I think if/when things start to get better without a backward slide like last year, pressure will increase to go back to the office, at least some of the time. I think a lasting legacy of covid will be more WFH, for some full time, but I think a lot of employers are starting to recognise the issues around team building, networking, water cooler ideas, mentoring and new starters. I've no doubt that productivity has increased for some but it has fallen hugely in lots of areas (try getting anything done that involves solicitors).
I can see it in my industry, where management are in one day per week each on a rota basis. On paper they can work from home effectively but they are so disconnected now from what is happening on the ground. From operational issues to the general mood of the front line staff, they have no idea. If I pop in to their office and my manager isn't in because it's not his day it's not always easy to get what I need from the manager that is in. It's not their fault and the plans were made to follow government orders so I'm not having a go, but it is demonstrably not working for us. However, the managers like it, so I imagine will resist being brought back to the office more frequently. They did always have the option to work from home, and can manage their hours anyway, but I suppose culturally most work was done in the office. I can see them doing something like 3 days in, 2 days WFH on a rota basis maybe.
I don't know much about it but aren't there liability issues for employers in terms of occupational health for people working from home? As others have touched on, you can't expect someone to WFH permanently when they're in their early 20s living in a house share.