They'll never, ever come down because there are many financial instruments tied to rental price. If the rent ever comes down there will be a cascade of negative effects where the owner needs to put up more money because the property is worth less. Since they're basically broke (yes you can be wealthy and broke) because they've borrowed a ton of money against the property and have put it in other investments, they don't have any cash and lowering the rent will ruin them.

Old-fashioned supply and demand is no longer in effect. They'd rather keep the properties empty for a decade than lower the rent one cent.