What is your definition of "replace"? Waymo operates a driverless taxi service in Phoenix. Sign ups are open to the general public. IMO this counts as replacing some drivers as there is less demand for taxi service in the operating area.
According to this article[1], the number of ride hailing drivers has tripled in the last decade.
I think full self driving is possible in the future, but it will likely require investments in infrastructure (smarter and safer roads), regulatory changes, and more technological progress. But for the last decade or so, we had "thought leaders" and VCs going on and on about how AI was going to put millions of drivers out of work in the next decade. I think it is safe to say that we are at least another decade away from that outcome, probably longer.
https://blog.waymo.com/2020/10/waymo-is-opening-its-fully-dr...