I'm going to predict that this will not happen. More specifically, that it will be unusual in general for rents or prices anywhere to drop any more than 10%.
There's something odd going on and my best guess is that there are (a) accounting/tax practices that provide incentives for vacancy with certain nominal values and (b) real estate markets are now driven more by massive pools of capital trying to soak up opportunities than they are by demand on short-to-mid-term horizons.
But I don't know enough to say for certain and explain how, and I'm hoping that someone can tell me why/how I'm stupid.