The ARM chip is used in every device that needs a CPU except the Mac.
With different iPhone, iPad, iPods, AppleTV models on the way, it makes sense.
If they can come up with a reasonably priced 4K TV set they would own the Market.
It would essentially be a large 4K screen with an AppleTV integrated. No UHF and VHF antennas needed. It's like an extra large iOS/ARM based iMac.