Some of the earliest uses of direct injection in production cars were Japanese makes in rather pedestrian sedans. VW went all out with direct injection around 2000 in their 2.0T engine, which is available in every car (except the Toureg) they sell in the US, ranging from the Golf, to the Tiguan, to the CC. I would not be surprised if VW sold the greatest number of direct injection engines in the world.
By contrast, Ferrari just started using direct injection in 2009. BMW just started using it in 2006. Despite the image we're sold by performance brands, they often lag behind in technology, simply because they don't have the budgets to do the R&D. They leave that to the big guys, then license the technology once it's been deployed in large numbers.
The article (which I mostly just skimmed) seem to center on technological solutions. But since CAFE is a fleet average, I wonder if makers won't just throw an EV or two in their lineup. With an EPA rating of 99mpg or more for EVs, that ought to bring the average right up. I guess that means people still have to buy them, though.