I also question the value of genius at driving GDP growth indefinitely. Eventually you run into natural laws that are insurmountable; you can’t genius your way out of entropy.
That said, the GDP wall could well be millennia away and we still have tons of room for growth. Maybe we finally bring cheap fusion online, solve asteroid mining, and terraform anything remotely habitable around us. Or maybe we don’t, investment as a vehicle for income fails, and no one gets to retire in 50 years.