Apple TV already has no reason to support CableCARD - They are already on the a la carte model. You can buy/rent episodes and season passes for current shows from iTunes.
Try this:
add up the cost of even just renting every episode of every show you watch now from iTunes.
Now compare that to your current cable TV package.
Now imagine your cable company went straight a la carte and allowed you to drop all but the "lifeline" channels (OTA feeds and probably some public-access type stuff), bringing your bill down to $20/mo or so, then you watch everything not on the OTA networks by either paying extra per channel or for on-demand.
Which of the three is really cheaper? If you follow a handful of shows religiously, you might be better off with OTA or lifeline + iTunes. If you only watch a handful of cable channels, you might save with the a la carte option a lot of people seem to want. But if you record a lot of different stuff so you have a variety of stuff to watch, you're probably better off with a cable package.
Where I am, the basic HD service doesn't have a whole lot of junk. I hear FIOS is even better. Getting a 4-tuner Ceton greatly increased the value of basic cable, and Comcast doesn't charge me for the CableCARD. Adding an extra TV means buying a used Xbox 360. That's it.
I personally would like to do package+a la carte. To get a few more channels I want (Science Channel, Nat Geo, BBC America) I need the "preferred" tier, which means I would also be paying for a lot of Encore/Flix-type movie channels that are made worthless by Netflix.
Hear that Comcast? I don't mind paying for cable, and I WANT to give you more money, but I want to only pay for the "preferred" channels I'll watch.