Considering that commercial housing started in PRC in the 1980s and the first batch of houses aren't technically expired yet, I think it's pretty hard to say what exactly will happen.
Come the 70 yr renewal, if there are citizenry who are attempting to disrupt the power structure of the CCP, they will be the first to lose their lease (or some other method such as a high tax which is equivalent to losing the lease).
Mark my words. Regulation that is not fully well specified, and enforced universally, is basically just a political weapon.