Idle speculation department.
I'm currently temping at a CPA office. Well trained professionals in this place. There's a good chance that some of the employees, at least at the executive level, are actual millionaires. Some of the customers definitely are, and some of them drop off their tax paperwork in person.
In the weeks I've been working there, I don't remember seeing any of the men who work there in suits. Someone who came in for a meeting, but that's a rare exception. And a couple of women wear what could be called suits, but female formal/office wear is a more flexible concept. The men may wear the same jacketless slacks/dress shirt combo I do, if more tailored. Or, occasionally, just a homey jeans and sweatshirt thing. I don't know how much of this is "WFH" comes to the office, a process accelerated by COVID lockdowns. It could also be part of a more gradual process.
Men's style blogs and magazine articles sometimes venture into "what comes after the suit." It tends to be the old standard, but less of it. Sometimes the blazer-over-tee look that I associate with Paul Simon.
My educated guess is that the suit will survive for some time longer as a formal standard of menswear, albeit more honored in the breach. This will hold until some other costume is formalized to replace it. Which doesn't show signs of happening just yet.