Everyday people lose access to their wallets, send Bitcoins to wrong addresses. It results in Bitcoins being lost forever. In the meantime, there is no way to prevent it.
So, lets suppose that Bitcoin would exist forever. It means that at some point there wont be any coin left in the network
I know there are other implications/discussions about Bitcoin supply. But Id like to limit this topic to this concern (Bitcoins lost).
Is the 21M BTC supply promise realistic?
i do not understand your question, it is not realistic, it is real and immutable fact, so yes that is the final number, which cannot be changed...
if all of us loose their access to respective wallets, there will be few BTC left, but supply will not grow, that is for sure