There id no such term as 'lost forever' for bitcoin. Because private key is shared by many people. Someone may have the pk of satoshi wallet by 2050.
Nope. The whole premise of Bitcoin is that the probability of that happening is so small that it is virtually zero.
A low probability does not mean it will not happen because it will. The more user of bitcoin there is the more often will this happen.
I would guess that a lot of computers are adress mining today. Eventually they will find something worthwhile.