Don't the ad blockers disable Google Analytics by default? If I am not wrong, I think uBlock Origin does.
So, I think, as more and more people will start using ad blockers, site owners will start getting less and less accurate stats from Google Analytics, forcing them to implement their own solutions. Hopefully, open source solutions will start providing the best features that Google does.
Anything that is widely used (open source or not) will be blocked because of common names or other patterns that can be recognized and blocked. If you need exact statistics you need to roll your own sooner or later. Or at least heavily customize some other product.
So, I think, as more and more people will start using ad blockers, site owners will start getting less and less accurate stats from Google Analytics, forcing them to implement their own solutions. Hopefully, open source solutions will start providing the best features that Google does.