It will be sold to you at a heavily subsidized price from a service provider looking to lock you in to a multi-year contract.
Because Apple can't build their own pay TV service. Nor can they launch an internet only service. Just like the iPhone, someone else owns the pipes: in this case it is likely to be the same company that provides pay TV service.
And if you own the pipes, you can make using lots of bandwidth to watch someone else's pay TV service really expensive and inconvenient.
If you are Apple, going through a specific pay TV provider allows you to have all the control you had over the iPhone. You can design the interface and do all the branding you want. Because if anything goes wrong, consumers will blame the pay TV provider. Not Apple.
It's a business model that will turn the TV industry on it head. And likely be very good for consumers.
Televisions used to be the sort of device you kept for ten or fifteen years. But with all the innovation going on from the manufacturers, you'll want to upgrade your television about as often as you upgrade your... iPhone.