Planning for the inevitable. I would not want to be "that guy" who sold an expensive HDMI solution using the limited wiring available, to help the guy not have to tear his room apart to fish new wiring. A savior, so to speak. Only for the customer get excited about UHD Bluray, buy a player a few movies for Christmas, only to find out, he is hosed and needs an even more expensive solution. :)

Now if you explain to him all of this up front, and he understands that he may get hosed, and he signs off on it, releasing himself from becoming a total douche to you when the time of hosing occurs, then go for it. Sell him something now that will work now, and then when he NEEDS 4K, he can cross that bridge when he gets to it.