sound card business wont die in years to come, just because you or couple of your friends dont use it, doesnt mean no one does.. there are millions of people who work with audio/sound and require excellent quality, i dont know any motherboards which can offer high quality with its builtin SC.. not to mention millions of enthusiast, myself included, who enjoys perfect sound..
of course the market is not as big like for motherboards, but its certainly not small and not dying

could be quite accurate for valve fans.. and 1 million users is a small amount at global market