Sanderson estimates he’ll start book 6 of Stormlight in 2033. He’ll be 57 years old.

It took him 14 years to get from book 1 to book 5. There’s no way he has his current motivation stretching into his 70s, especially as his works (I assume) will start getting adapted and suck up that much more of his time.

Either way, the man’s bibliography is going to be legendary. I just have my doubts he’ll be able to get through book 10 (which is allegedly supposed to be the end of the Cosmere)