Five to ten years? Much faster than that!
The pressure on cities to house bums, druggies, and invaders is intense. Have you seen the pics of what they do to upscale hotel rooms? They are ruined in WEEKS.
I suspect some city tax-revenue people will argue that if you give up on office space...you will never get the ultimate tax revenue level back.
Another argument (particularly in SF)...what little commerce you have left, if they know what your plan is...massive shut-down of grocery/store-fronts will start up. You might find a 20-block circle where no coffee shop or grocery exists near a designed ghetto section.
All you are designing is a release for the stupid owners or banks left holding the non-use office building or hotel.