This appears to be a case where the landlord wants the tenant out, perhaps to live in the unit himself, or perhaps to sell it as a vacant unit, but for various legal reasons it's impossible or unattractive to take the simple path of saying, "I decline to rent to you anymore", and the landlord instead is going with the effectively equivalent option of raising the rent to approximately infinity.

I don't believe they expect the current or a future tenant to actually pay $8000/month. It's conceivable that they might lower it to far below $8000 as soon as the current tenant is gone, and then rent it out to someone else -- maybe the landlord just doesn't like this tenant.

Of course, none of this is allowed in a rent-controlled unit, and all pre-1979 apartments in San Francisco are rent-controlled, so my guess is that this hundred-year-old multi-unit building is actually a set of condos, and the owner of one had been renting it out to this tenant; in such a situation, rent control is generally not in effect, for the same reasons it's not in effect when one is renting out a single-family house.