They even haven't built an FM radio into the iPhone yet. So why would they try to do that tuner thing in a full blown TV set ?!
It would have to be a TV which is totally different than current ones, stripping off all the hassle with tuners and various input sources. Just the LCD panel, wifi and AirPlay receptive A5 or A6 equipped logic board. No hardware scaler, no 3D processing, no HDMI ports.
If they could produce at 300$, they had to sell no lower than 600$ to get their standard margins. And Apple should never drop their margin targets!
But, who would buy a TV set without inputs and tuners ? I guess, even the hardcore Internet enthusiasts among us would not consider that. TV is all about 'having all possible options'. sports events, night shows, p*** channels, kids program ... I don't think that Internet can compete with the current 'old school' TV model. Just iTunes, YouTube, Vimeo and the like without anything from the 'old world' ? No one would buy it.
It would be sufficient if they license out AirPlay, create a reference standard and leave it to a 'coalition of the willing' original TV set makers to bringt that to market. A fully equipped TV with an included AppleTv logic board would do it. Apple could describe all of the user work flow integration in their reference standard, e.g. require that the TV switches on for AirPlay and the like. All Siri remote control can already be done by iPhones, iTouches etc.
Also I think that an iTV would cannibalize some iPad sales, as the iPad is also a good home video consumer device. And how would an iTV integrate into the ecosystem ? There's nothing more passive than a TV screen, neither touch it, nor want to see apps running on it, not even 'widgets' ! That has all failed. Would Apple sell more content ? Probably not. And whats todays revenue contribution of iTunes ? iTunes is there to support hardware sales, not other way round.
'Reinventing' the TV only makes sense when you can reinvent its content. But who wants that and how profitable is it ? TV content used to be 'free', paid by ads. So this is Googles territory.
Home automation would be a much better Apple target: it's essentially hardware, it's a mass market, requires cloud and networking, integrates well into iDevices, requires extreme user friendliness ... and as it controls your home power, could refuse to recharge/supply Android devices...
And it's for people with money. I don't see that Apple should try to serve to all the freebies.