In S. Korea, Hyundai has been very successful marketing the "premium segment" of their automobile line. That's why their higher end cars, such as the Genesis + Equus (which has been out for quite some time now -- not the concept sketch in the link above) carry different logos. I do agree that Hyundai has a few hurdles to jump over before they can eventually enter other traditional markets, such as Europe, China, and Japan, but I don't agree with you completely about Lexus not being successful in those regions. When I visited Hong Kong and S. Korea, I have seen quite a few Lexus cars on the road. It's weird though, I never knew Toyota (which is quintessentially Lexus) had an SUV that looked EXACTLY like the Lexus RX -- which was affluent all throughout HK.
Also, i must disagree w/ S Korea being more open to alternative & cheaper premium brands... yes Hyundai is considered amongst the lower automobile tiers in the US, but in S. Korea, a Sonata goes anywhere from $35-50k. I also haven't seen any hondas, mitusbishis, nor any american cars during my visit last summer.
In all, I wouldn't be surprised if Hyundai introduced a luxury line, like that of Acura, Cadillac, Lexus, Infiniti in the US in the next decade.