It is not right to assume that all BTC will be lost as more and more people have become aware of importance of BTC and they will take extra care to keep their BTC safe.
But yes some of it will be lost for various reasons but it is good as overall supply will decrease
bitcoin supply will never decrease even if some Bitcoins are not accessed and abandoned by the owner. We don't know who doesn't have access to their Bitcoin assets and how many.
Bitcoin is the most valuable digital currency asset today. Some people even have plans to pass it on to their children and grandchildren. There are many methods that can be done to keep these assets moving and can be accessed by people they trust.