99.21875% will be mined in 20 years time. If electricity isn't very cheap by then and/or if bitcoin isn't worth hundreds of thousands of dollars, it's hard to imagine anybody wanting to mine then. How will transactions then be verified?
Let us see if bitcoin still alive in that year for me even the cheapest electricity can mine bitcoin we are always depending on the hard we are using if we are using much more powerful hard mining then we can mine more bitcoin in a day in that year and we know that every year there are upgrading.