In time we will have fewer and fewer bitcoins, currently it is thought 3-4 million bitcoins are already lost. This makes me sad.
This should not make you sad because it means that the coins you hold become more valuable. The fewer coins on the market, the more valuable they are.
I am aware of Satoshi's view on this "lost coins are a donation to everyone". Yes, but 4 million is a lot,
Who says 4 million coins are lost? Who can even say for sure?
do we want Bitcoin to still be used 1000 years from now? If this trend continues most if not all bitcoins would have been lost by then.
Do you really care what will happen in 1000 years? Will humanity exist in 1000 years?
Again, this is an approximation, but 4 million lost coins out of 21 million. That's like 20% of the total gold/fiat supply just vanishing forever.
I still don't see where the problem is? Would it really be a problem if 1 BTC was worth, say, a million dollars? Or more. After all, each bitcoin can be divided into 100,000,000 satoshis. So, if a bitcoin becomes too valuable, there's no need for anyone to handle or transact with the entire bitcoin unit.