This would only be valid for content originaly shot at a native 4K resolution. Also movies shot on film will need to be rescanned and restored at 4K resolution. There is no point of re-encoding content that is not native 4K or better, because the Apple TV (to be) will do that job anyway.
I recently bought a 4K TV on black Friday so, yes, it does matter to me. Is hard to switch back to 1080p after watching those gorgeous graphics in movies and tv series. My smart TV has youtube and netflix, both support and broadcast content in 4K, a beautiful thing; even another reason to skip Apple TV 4th gen. I will settle with my 3rd gen until then. I guess Apple loves to crash into parties very late.
It needs time. Like I said before many 4K sets include a hard drive with 4K shows and movies. No 4K Blu Ray are out now. For the price of 4K sets yes most people should purchase one for the small difference between it and a smart tv. They have t wait for the connect though.