Look twenty years out and it appears vertical. But 10 years from now it will look much flatter, and what's then 20 years out (30 years from today) will look vertical.
The grass is always greener 20 years in the future.
It's the difference between a differential equation like x' = x and x' = 10x . In either case you can say "meh, if you normalize on today's value, the increase in 10 years is just a constant multiple", but the transition from one phase to the other will still be noticable, even though things won't "go vertical".
Even then, we're undoubtedly going to see some really amazing stuff come out of machine learning in the decades to come, just maybe not the beginning of Ragnarok.
Try as I might, I probably couldn't put it better than it's done in this talk: http://idlewords.com/talks/web_design_first_100_years.htm
What actually happens at that point, I think that's up for debate. Are we going to become immortal? Probably not. Are we going to have AIs who are better at everything than expert humans? Probably not.
But I think it's strange if someone denies that it's even happening. Just look at the amount of information that's flowing around, by any metric. It's exponential, and you can fit the curve and plot where it goes vertical. If we were talking about physical processes, I'd understand the skepticism. Maybe that exponential levels off. But I don't see why there is any physical limitation on how much information can flow. Or at least: if we hit that wall, things will be VERY different.