It doesn't really matter what the life expectancy is/will be Sloppy as the HK government will just lie about it as they do with most other things.
Do they inform people that around 2000 people die per annum as a direct result of the air quality ? No they don't. ( it's 7 figures in China )
Let's face it, neither HK or China can afford to be honest about the pollution so it is left to the individual to vote with their feet.