One tidy option that requires you to buy more apple hardware (apple rule 1 - you haven't bought enough till you're a catalogue) that I'd like to see is iOS -> TV -> A lot of cable/etc boxes. I believe you can do various sorts of control through HDMI, and the cable box makers would want to help Apple.
Speaking of h/w, I think Apple could make a killer flat screen TV. Heck, some of their current monitors are almost there already. Now, integrate that with your iPad, iPhone, Macbook and Apple TV? Add great content and a few million apps designed to make the who experience amazing. I'm in!
I have a Sony HDTV, and a Sony dvd/hdd both with freeview, I don't really know the troubles of a cable box.
This is a distinct possibility. I believe Jobs is on a secret mission to destroy the hated cable tv box remote, the curséd one-thousand-button behemoth.