According to an article by Blockchain Council, all 21 million of Bitcoins will be mined by the year 2140. almost 120 years from now. Bitcoin supply will be completed and then miners will only earn money by confirming transactions. and earn fee from the fees.

This article is very interesting you can read it here: https://www.blockchain-council.org/cryptocurrency/how-many-bitcoins-are-left

Now for your second question. I don't think there is any point in thinking about that. because that's not realistic. I don't think all bitcoins will be lost. there will always be Bitcoin in circulation. it will just get harder to get it because it's price may increase so much with time.