Author here, copied from another comment above.

Actually I doubt we'd have picked 27-bit addresses. That's about 134M addresses; that's less than the US population (it's about the number of households today?) and Europe was also relevant when IPv4 was being designed. In any case, if we had chosen 27-bit addresses, we'd have hit exhaustion just a bit before the big telecom boom, a lucky coincidence meaning the consumer internet would largely require another transition anyway. Transitioning from 27-bit to I don't know 45-bit or 99-bit or whatever we'd choose next wouldn't be as hard as the IPv6 transition today.