Read an article once, author claimed up to 30% coins are lost forever.
I wouldn't go that much or believe that article like most of them, but there is definitely quite a lot of coins missing/lost would you count satoshi's million+ as lost as they have never been touched for years? I am guessing anywhere from 10-15% but who knows and in the future there will obviously be a hole lot more being lost which is good for everyone else who doesn't lose them i guess them, smaller supply higher value.