According to a Reuters report, Hyundai "fears a proposed tax on vehicle carbon emissions will slash its domestic sales by up to 10 percent." The article adds, "While some experts say the warnings could be overblown, they are a stark reminder of one of the biggest challenges Hyundai faces - how to make greener cars to ward off competition from more fuel-efficient rivals."
Adding more fuel to the fire, so to speak, is this quotation from the article, "[Korean] [c]onsumers have developed a particular taste for diesel-powered vehicles made by the likes of BMW and Volkswagen that have greater fuel efficiency than Hyundai's mainstay gasoline-powered vehicles."
That could mean Hyundai will start developing more fuel-efficient products for the U.S. market, including diesel powered vehicles. Of course, maybe that's something only an auto enthusiast pushes for but given Hyundai's reputation for innovation, any diesel products it introduces for the U.S. market would bound to be appealing to a wider market because the company would probably offer it at a good price.
Also, a drop in demand in the domestic market could free up more product for the U.S. Hyundai is going to introduce two instantly popular models this year: the Genesis and the Sonata. Demand is going to be strong. Less demand for the home market would make both models readily accessible. Production constraints would not be an issue.
And, lets face it, more green products from Korea helps all American consumers because it puts pressure on Japanese and domestic manufacturers to stay competitive in terms of both innovation and pricing.