So...software engineers become product managers? All of us? That's going to be an awful lot of product managers.

More like architects, in the civil engineering sense. Even if you don't pour concrete or drive nails yourself, you have to have a lot of technical understanding, including the low level, to be able to design a building competently. And, very certainly, you have to be able to inspect how the nails are driven and how the bricks are laid, whether your contractors are humans or robots.

Or it could be an awful lot of productivity. We have to think bigger. What would the world look like if every programmer were a 10x (or whatever) programmer?