What are your thoughts?
I can think of four reasons against a premium/luxury Hyundai brand in the near future.
Hyundai autos include more standard safety features than anyone else, including the premium/luxury brands. Historically their cars have provided numerous luxuries. They do not have an economy car image to overcome (probable reasons for Acura, Lexus, and Infinity). Warranty is already superior to the luxury brands and not just in America, but throughout the world.
Wisely, Hyundai focused on reliability and has nearly overcome any bad perceptions from the past. Hyundai and Kia already have two brands and dealer networks without the cost and risk involved with creating another brand. Slowly they are advancing distinct brand directions: Kia in a sporty, youth-oriented, fun direction and Hyundai in a luxury, conservative, safe one. Hyundai's worldwide R&D is filing a record number of patents. I suggest they market technology as an additional thrust for the Hyundai brand -- it's more exciting than conservative and it fits well with the safety and luxury direction.
Hyundai has a knack for efficiency and already surpasses the other guys on this mark. I really hate to see them lose that advantage with the extra cost involved in launching a new brand (or like Toyota an additional third youth brand).
Last, I fear a luxury brand will introduce an unavoidable negative side effect: a change of attitude. Hyundai has fostered a care for the customer and do what is right attitude from top to bottom. What I have heard, read, and experienced personally leads me to believe this could be altered in an environment with premium branding.