Well hey, Hyundai is stepping up their game, particularly with powertrains. The new Sonata matches Accord and Camry for engine choices, and the Azera has plenty of power as well although it gets there with a bit more displacement. They've already moved well past Detroit, that's for sure. Hell, even Daewoo is moving up--they're going to be supplying a good deal of GM's small cars all over the world.
You have to remember that the Korean companies got a late start to the car game. They've still got some catching up to do to be on par with the likes of Honda and Toyota. But if you look at the electronics business, companies like Samsung and LG are huge powerhouses even in premium segments whereas 10 years ago if you said to someone, "hey check out my kickass new Samsung TV," they'd a been like, "Sam-huh?". I think the folks back at home base are being a bit overambitious with wanting to hop up to the luxury market sooner rather than later, but the people running their US operations aren't stupid and I think they will try and delay that until a more opportune moment.