Not fully convinced by the "will make fares lighter for everyone else" argument. The economics of planes are heavily weighted towards the passengers up front - business & premium economy make more profit per sqft for the airline than seats at the back. So I'd imagine that a reduction in demand for premium seats could actually increase prices.
The flipside of this is that the passengers in the back, while not as profitable in the "$/sqft" equation, are what merit the airline buying a 777-300 or A350.
If all your focus is on those premium passengers, then you don't need as big an aircraft, and you end up with things beginning to approach JSX's (https://www.jsx.com/home/search) mode of operations.
