Not quite. First, keep in mind that we're talking about two things in this thread: (1) Over-the-air and (2) cable. With regard to over-the-air, there is a deadline, it will arrive, and then you will have had to have done something by then, or you'll be watching snow. With regard to cable, nothing is set is stone yet. The Order issued by the FCC on Friday was limited in scope and didn't mandate anyone switch to digital. Rather, it just made it very clear that the FCC will be doing things to provide cable companies substantial incentives to make the switch from analog or hybrid analog/digital to all-digital. That, combined with the fact that at least one cable company has already made the switch, city-wide, in a major American city (Chicago), without any FCC incentive provided, makes it very clear which way the wind is blowing. However, remember, it is not set in stone, yet.
Also, note the distinction: Is isn't that you will have to switch. Rather, the cable company will simply stop offering analog service.
Presumably, if you're paying them for service, you'll want to buy the equipment you'll need to view the service you're paying for.
I'm not sure what part you're confused about. Are you wondering why the cable company would switch to all-digital service? That I can explain.
First, as I indicated already, the FCC will probably be providing various incentives to do so. The first was that if they pledge to go all digital by December 31, 2009, then they are exempt from an Order to provide separable security in their cable boxes. Don't worry about what THAT means, but rather just understand that the waiver saves them a lot of money as the boxes they will be using will be less expensive than the boxes they would have had to use if they didn't get the waiver.
Second, in order to provide an analog channel to you, it takes up 6 MHz of bandwidth. A typical cable system has between 550 MHz and 800 MHz of bandwidth. So at 6 MHz per analog channel, they are limited to a total of as little as 91 channels, and that's assuming they use the whole pipe for television; in reality they have to share that pipe between television, Video On Demand, telephone service and high-speed Internet service!!! In this competitive marketplace, the most profitable customers choose the cable company that can deliver them (literally) hundreds of channels. A digital channel provides typically BETTER picture quality, but only requires 0.5 MHz of bandwidth. They can fit 10 superior digital channels in the same bandwidth as just one inferior analog channel. So switching to all-digital helps them offer hundreds of channels, better picture quality on all of them, plus all the other services.
Does that make sense now?