I had a similar thread going. Unless you happened to have some critical Apple type thing going on (and I can't imagine what) there doesn't seem to be any reason to buy one now. Very outdated.
AirPlay. That's enough to justify buying one, depending on what you had before. We needed TV 3s for work in order to facilitate BT connections without first logging into the wifi network. TV 4 is the only option now. I have an TV 2 at home I need to upgrade, but waiting on 4K, despite the frustration of having to log friends and family onto my network before they can stream to my TV. Its sad Android using F&F can stream to my 4K smart TV easier than those using Apple, but that's a little on me. If it happened more frequently, I'd have upgraded by now. But 720p is more than satisfactory for streaming video and viewing photographs, especially with the up scaling abilities of my 4K TV, and much easier on the bandwidth when streaming. That said, now that I've gone 4K, I'm eager to start using 4K HDR whenever it's an option due to the amazing picture quality. So Apple is losing money from me -- I'm renting UHD HDR movies on Amazon now instead of through my TV. And for those who say there's no content, I'm happy to report there's plenty for the new movies arriving in home video I want to see, with more and more being added everyday.