Typical length in cities (so where people have the longest commutes and are most likely to use public transport) is about 3 years, and within that, there’s usually about a year of searching and negotiations, so even firms who are tied into a particular office until spring 2023 will be thinking about what they want to do beyond that.
I’ve mentioned it before, but I do think that the changes forced by Covid have broken through a lot of the latent resistance to remote and flexible working, and I don’t think we’ll ever see city centre offices returning to anywhere near the levels of occupation that we were seeing in February.
That has huge implications for things like land use, local facilities and whether certain places just will not be able to trip over the threshold of gaining from the benefits of agglomeration. Sure, you might be able to work as productively at home doing your office-based job, but the other benefits of cities (eg cultural, shared networks) might end up becoming untenable if so many people have relocated.
I think that there are great benefits to be had if we shift to a ‘15-minute city’ model of living, but there’s a danger that it’ll instead just turn into a reversal of the Great Inversion, and people will move out to clone town, low-density car-oriented hinterlands.