Last BTC should be mined somewhere around year 2140, but this is just information that we should not worry too much. More important thing is to know that almost 99% of all BTC will be mined around year 2032, so we can say that in some 14 years from now and even before we can expect very small amount of fresh mined coins on market. Considering halvings in years 2020/2024/2028/2032 we can expect that price will go up to a significant extent if demand increase over the years.
Exactly, we really don't need to go and see the last bitcoin mine, because technically by 2032 we can say that 99% of it will be mine already so its obvious that as speculative asset we need to hold and buy cheap coins and just let it sit in our wallet for the next decade or so.
The problem regarding BTC quantity and last coin mined arises because of ignorance, year 2140 is so far away, and for us who live today this information is completely worthless. We have a year which is much closer and mostly achievable for everyone, so we need to focus on that. Many positive things will probably happen in the next 10-15 years, but we all know that law of supply&demand has a very big impact on the price.
If people know how close we are to the point when 99% of all BTC will be mined, they might look a little differently on the whole situation. I bet some 10 years from now people will discuss about cheap BTC back in 2018, same as we do today about 2010 or maybe 2014.