given that very few companies pay for J these days, and J is now a high end leisure product, I wonder which airline will take the chance and remove J entirely?

Companies will absolutely pay for O, which is why that cabin is often oversold by a large margin (at least on UA)

To cater to the high end leisure travelers, maybe add back an F cabin. A F-O-Y config (maybe go to something like 42 inches of pitch for O to further differentiate it from Y, but keep it well below F so that we don't have the lack of differentiation we had between J and F of old days