Desktops and laptops from 10 to 15 years ago are basically all 64 bit. By the time this removal happens, we'll be at 20 years of almost all that hardware being 64 bit. By the time hardware becomes "retro", you don't need the latest kernel version.
Lots of distros already dropped 32 bit kernel support and it didn't cause much fuss.
20 years isn't all that much though. We maintain houses for much longer than that so why should we accept such low lifetimes for computers.
Ten- or fifteen-year-old hardware is still perfectly serviceable now for some modern applications. (The decade-long Intel monopoly drought of 5% generational improvements to CPU performance has a great deal to do with that.) So this is not as strong of an argument as the same sentence would be if it were said ten years ago.