My questions is that ' is there any possibility that some point in time in future BTC community might decide something which can retrieve this lost BTCs?
How do you know these coins are lost? Maybe they are just "holding" these coins? BTC community can't do anything about this at all. The system is decentralized and immutable. Meaning you can't retrieve lost coins and you don't know if they are lost in the first place. This is the beauty of blockchain. A mistake or not, once it is done, there is no turning back. People may try to fork bitcoin off but all they'll have is a worthless chain which nobody will be using.
He instantly assumes that the coins are lost just because they are untouched for 5 years now but you can be right with that. What if the coins aren't really lost but what if someone is just holding them? They are not an ordinary person like us that are emotional and can easily sell our btc when we see a small dump or pump in the price but they can be big institutions or whales whose aim is to hodl for a long time to reap maximum benefits since they already figured out the potential of btc.
The guys prolly started buying and hodling btc on the year 2017 because if we will count it, that will be exactly 5 years up to this date we have now.