Think about it. Apple already sells 30" HD displays (which will set you back $1,799), you have iTunes pushing out movies and TV shows, and the company has already dabbled in home entertainment with Apple TV (a product that has a lot of potential, most of which is currently unfulfilled). To top that, Netflix plans to have streaming for Mac online by the end of the year. Breaking free of the computer and portable media market and expending into a new market makes a lot of sense.
After all, it's not the first time that Apple's broken into an existing market where the current players are all asleep at the wheel and shaken things up a bit - think iPhone.
Whether you or I love it or hate it, the key to Apple's growth is iTunes. People on the whole love iTunes. Apple has built a framework that allows them to rake in money and customer loyalty through dimes and cents transactions. Any HDTV that Apple might be working on is going to be a lot more than any other HDTV on the market. It'll be a breeze to set up (Apple's got the knack of reducing cables and sockets down to a minimum), it'll integrate with other Apple products (iPod, iPhone, Macs ...), and my guess would be that Apple will integrate iTunes directly into the set (and more than likely offer a model that incorporates the features of Apple TV). Oh, and it'll exude cool and all Mac fanboys will rate it as being about a million times better than any other TV ...
Home entertainment companies be warned - if Apple really is planning on entering this market, then get ready to dramatically raise your game.