AI Completionism?

I'm reading through "The Age of AI" and I'm wondering how long it'll take, realistically, for AI to replace humans entirely not just as workers but as thinking beings. In other words, to reach a state of simulated human-like intelligence where humans no longer have a purpose beyond historical entertainment. I know AI is making strides in the workforce and art but how long will it take for it to get to the point where humans are genuinely obsolete?