To know how much bitcoin have permanently lost can be impossible for now, but probably after many centuries it will be possible, the untouched bitcoins can be assumed to have been lost, using addresses connected to it for the tracking. But right now, the amount of bitcoin lost can not be known.
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 