With the surge in Ad Blocking recently, part of me wonders how accurate the Google Analytics JavaScript tracker is today, and how accurate it will be in 5 years. I wonder if we'll see a trend back to server-side analytics soon.
The percentage of visitors with an ad blocker depends on your site's audience. Outside of computer geeks and gamers, almost no one uses ad blockers. I wouldn't buy into the hype that the whole world is installing ad blockers.
[1] https://pagefair.com/blog/2016/mobile-adblocking-report/