I'm not sure there will be an traffic Armageddon. I don't think commuter traffic will come back to pre-pandemic levels. Boston traffic has been awful for several years. I agree there will be issues getting workers to jobs but that's because I expect jobs to be more distributed away from city centers.
I think the impacts will vary greatly in different industries and jobs. Waitstaff, cooks, bartender, plumbers, electricians, retail, hairstylists, etc....demand will be up in the burbs and down in the city center. Short and long term.
White collar office workers, hybrid WFH/WFO, full WFH and a few in full WFO. The economics are too compelling. We are shutting down office space. Talked to a financial services person who worked downtown, they are going from like 10 floors to 3 in their building. Then you add the reduced commute cost and time savings to employees. Reduced electricity cost. Any productivity lost is easily made up for by massive cost savings. Companies that don't offer at least hybrid WFH are doomed. Loads of reports of people just quitting when asked to go back full time.