This could easily be an OS that is licensed for 3rd party manufacturers, like Airplay. Most people would be shocked to see Apple have its own branded TV, as that market is tough. Let Toshiba, Sharp, Sony, etc. carry the burden of selling the TVs themselves, and let Apple take $100 in licensing fees per set.
The day Apple licenses an OS again is the day Apple's rise ends. Part of the rebirth and success of Apple was when Jobs killed the Mac clones.
Apple will probably just use the parts from Toshiba, Sharp, Sony, Samsung, etc... but they'll make their own set if they actually are making a set.