Re: I would hate to own commercial real estate
"Fewer people will want to live in the big cities if they're working from home and commute time is no longer a factor. You can live just about anywhere so long as you have decent broadband."
Not everyone will be working from home. Mixing residential and business would make it easier for those whose employers are dedicated to presenteeism to avoid commutes.
AFAICS the growth of cities has been in overshoot for a good while now. Simply getting people into work in big cities has been a major headache for years, not helped, at least in the UK for town planning policies which, for more or less the whole of the post-war period, have been dedicated to separating residential end working zones. Just to add insult to injury for those condemned to long commutes, they were then blamed for causing congestion.
It's time to rethink. Don't build more offices in cities. Look at the possibility of shared work spaces in the peripheral towns. Move as many of those who continue to work in cities and are prepared to live there into converted ex-offices. And accept that even then there will be redundant space there.