Forget about an integrated TV...Apple should just release a large-format Thunderbolt display (50", 55", 65") optimized for HDTV content, along with a improved set-top box.
The display, being optimized for HDTV, would be a simplified version of the Thunderbolt display that's currently made for Mac. So, this would mean a lower 1080P resolution and less i/o features, but still a FaceTime camera and microphone and one Thunderbolt input (forget HDMI input and other inputs since it is made for interfacing with the Apple set-top box). With the reduced feature-set - hopefully that would mean a similar price for a much larger display.
The set-top box would be the hub for connecting whatever you would like to connect to the Thunderbolt display. And, could be more reasonable to update on a 2-year product cycle. So, your Thunderbolt monitor stays with you for a good number of years (like a typical lifecycle of a TV), but the set-top box gets upgraded from time-to-time as technology advances and keeps revenue coming into Apple.