I don't think we need to wait for centuries for something like that, probably the bitcoins that didn't move in the next 20-30 years top can be considered lost forever. I really don't see a single reason why someone shouldn't move a satoshi after 30 years, especially because he would be at least 50-60 year old at that point. Hodling till death is kinda extreme 
Here is a simple reason: you don't store all your bitcoins in one address and you don't have to!For example I started back in 2014 and I have some coins that I have not touched ever since then (that's about 8 years) and there is a good chance that I will never touch them for a decade or two. But it doesn't mean the coins are lost or I have not spent or sold any bitcoin.