The last bitcoin will be mined in 2140 or so, we won't live to see it happen and the world will be so different then I doubt we will even have a monetary system at all. At least not something that resembles anything we have now. Bitcoin will be long gone before that time, a currency's timespan is no longer than 40-50 years if you look at history. No reason to think it will be any different this time.
It may well be so as you picture it, but actually that was not my point... Some people here (and there) draw bright prospects for Bitcoin when and if it becomes a legal tender or a means of exchange. So I was trying to give some cogent reasons why this is not going to happen at all (as opposed to "just not any time soon")...