“brake pads, rotors,”
Actually, if braking loads are primarily regenerative, the rotors and pads last much longer. They likely would not need to be replaced in under 400,000 miles.
While I'm certain that regenerative braking could reduce loading on the regular braking system, I seriously doubt that it would become the primary braking source. Heck, I can bring my Honda down from 80 to about 5 mph purely by downshifting and relying on engine compression to slow the vehicle down, but that approach isn't practical for the most part. 400,000 is a stretch - 80,000 maybe. If you drive in a manner that takes the greatest advantage of the regenerative system.