I think you are looking at it from the wrong perspective. It will affect hundreds of millions of iOS users. Whether these users choose to use their newly given freedom to install software not controlled by Apple is up to them - but the legislation affects 100% of iOS userbase.

(in hindsight I shouldn't have said it will affect 0.0001% users - maybe I should have said that I guess only that many users will choose to sideload software instead)