Many asked before and I'll ask again: Why not let the user decide on a TV brand (be it current HDTVs or 4K TVs in the future)?
The TV is "dumb" in this scenario, all it does is display content via HDMI or wireless
I still think Apple should continue to focus on the AppleTV box and improve it. The user experience is great for setup, all it takes is a single HDMI cable and Apple can sell into millions of homes who already own HDTVs.
Apart from integrating a surround system into the TV like Bose did...
http://www.bose.com/controller?url=..._built_in_home_theater/videowave_ii/index.jsp
...I don't see any advantage in Apple selling its own large TV sets. Just think of handling, shipping and storage of these sets in crowded Apple stores etc.
Microsoft has great ideas in this area with the Xbox360 and Kinect, the new Nintendo Wii U also has nice features (control TV with the gamepad, "second screen" info, metadata, EPG...).
Unfortunately, Apple is falling behind in the living room in my opinion.