only a long passage of time or a continual increase in price can give you hints. 100 years plus from now there should be a pretty good idea how many are actually out of service forgood
Bitcoins can change hands without changing addresses, that is less common though. There is a couple million bitcoins from way back that is most likely lost forever, and there will be-
methods to determine the likelihood of coins being permanently lost that approximates the real amount over time.
they can change hand without changing addresses, but in any numbers that make a huge dent in supply, the receiving party would want the certainty of their own fresh private key.
