If I loose my wallet and the bitcoins in it, does that mean Bitcoin has forever lost those bitcoins? If people keep loosing wallets, it's not going to be 21 million Bitcoins in 2050. or what is the inflation end date.
You almost always have a backup from a few months ago and older backups have a pool of 100 "future" keys, so you recover everything.
Or, in 2050, breaking 40-year-old algorithms is a piece of cake, Bitcoin has already moved to better algorithms a few times, now people break older addresses and recover lost coins. It's a hobby for some.