The cable companies or Broadcasters (in the UK) will resist as much as possible. For they know that once Apple are allowed a tangible foothold in their industry it could be all over for them and they will lose revenue control, as they have with the Music industry.
I am not sure on this either way, but you will certainly just be exchanging one master for another in most respects. Personally, I am perfectly happy with my ATV, Sky (satellite/cable) subscription and my iTunes account as it is. In the UK we get free on-Demand TV from all the big 4 channels, we also get (without additional fee) live TV access via computer / iPhone & iPad from Sky TV. They even provide free apps that let you do this.
For those of you thinking that it will be cheaper if Apple gets involved, or that you will somehow have a significantly higher-level freedom and content, this is fantasy. Also Apple is not a content provider, unlike the BBC, HBO, FOX etc, so it not as simple as dealing with the content providers as some posters have mentioned.
Previous Apple involvement has shown that you will have to pay a price (not just fiscal), as they will control what they allow you to pay for and what hardware / features you can use. Drum roll for the ‘Apple Television set’…?
Apple will need to hope that at least one of the larger Broadcasters breaks ranks and sells them all out… Oop’s sorry I mean accepts a generous offer…
Things are different in the U.S.
Subscribers pay the cable company regardless of the maker of the box. Comcast doesn't make their own boxes. Just the really bad GUI software installed on the box. Because of this I don't think the major cable companies have much to fear from Apple except being one-upped on a GUI. They still control the media that comes from the studios.
From what I've read all Apple wants to do is make a better GUI on it's own box and integrate the cable companies media with what Apple has to offer.