From investor perspective, rental yield going down alone is not the primary factor of concern.
Let's say you buy a rental property, and get 6% yield a year. After 5 years, you already getting back 30% of the capital.
A 30% price correction will only set you back to square one and you are still getting return back every year in the form of rental. 10 more years and you will most likely be ahead of the game in term of profitability.
It's might be a good investment until it isn't. So it wipes out all of your rental earnings of the past 5 years.
When you see the prices being that high I don't think it's wise to invest any more. In fact, I'd be divesting instead. Because when it pops I might not be able to sell fast.
but i still have somewhere I can live, versus say bad share investment.