What will boomers, the richest generation, ever do?

This is overstated. The alarm was sounded on this 2 decades ago for several east Asian countries, but they're not on fire. They're fine. Old people die.

If the fertility rate mattered that much, they'd have scrambled to make any number of policy changes including better work-life balance (see: Japan, SK, China), or plain ol' immigration, but they don't because it simply does not matter. All the efforts have been completely half-assed (like tax benefits, cash).