I don't think there will be Bitcoin in 2140, because it will be fully exploited at some point. I believe that digital currencies will completely replace fiat currencies in the distant future, with the development of technology. But most likely there will be other digital currencies, not the ones that exist today. It's just a personal opinion based on imagination.
I respect your opinion but it is said that bitcoin will all be mined before 2140, some say it will not be before may be on or after that year. I do agree that there will be other digital currencies in the future but I don't think bitcoin will just be left out with a lot of supporters of it all over the world. I think at that time the price we have might not be he half of it.