The primary residence owners get the same perverse incentive to illegally rent and never sell the property. Why wouldn't they? It's literally free money.

And transfers don't need to happen when the average person lives 80 years. These units will largely be kept off the market for over thirty years.

I understand your concern about long time residents being forced out, but the proper solution to this is not locking out large portions of the housing market. A much better solution is to highly encourage new and higher density housing to make the area more affordable to everyone. Existing residents don't deserve to live in SF more than new ones just because theyve been there longer