It's not like the metric system was invented yesterday and will vanish tommorrow. Change doesn't have to be instantaneous, it can be gradual over the years (and, as the article pointed out, already is)
I agree that things won't change instantaneously, but I also don't think change will happen or even could happen as quickly as most of the talk on the internet thinks it should.
These articles make the rounds on the internet every few months, which gives the impression change should happen quickly. But, given the enormous costs that exist to switch over, I think it's more likely we'll see a gradual change over our lifetime.
Also, switching to metric units for measurement doesn't mean you have to switch the physical size of parts: there is nothing in the metric system requiring that you use round numbers in manufacturing. Canadian engineering, for a mixture of historical reasons and ties to the U.S., measures in metric but often has parts with suspicious sizes like 101.6mm.
I did a bit of work at NASA a couple years back, they wanted everything in millimeters (possibly to deal with the aftermath of that incident). Everything. Even antenna lengths.
These articles make the rounds on the internet every few months, which gives the impression change should happen quickly. But, given the enormous costs that exist to switch over, I think it's more likely we'll see a gradual change over our lifetime.