These things take a lot of time to develop
Apple was working on iPhone for 4+ years before they released it, there were rumors about an Apple phone for years but no one really knew what it was going to be. Many conceptual drawings showed it with an ipad clickwheel along with the inevitable numeric keypad. What is now an "obvious" interface for a smartphone was hard to imagine until Apple created something that simplified a smartphone enough for normal people to want one.
So the rumors about a TV running for a few years before a product comes out is reasonable, it is only quick to do if they make a regular TV set, slap an Apple logo on it and a mark up the price. So think about what is complicated with today's TVs for normal people? (keep in mind almost everyone reading this is not a "normal person" by my definition, i.e. we know how to wire up a TV along with a DVD player, DVR, games console and external speakers without reading the manual or calling Geek Squad)
Three things spring to mind. One connectivity - getting everything wired up properly. Two - figuring out what the hell is on when channel surfing and when recording. Three - having a bunch of remotes, or if those normal people have help from one us, having one remote programmed to control most but not all of everything your big collection does (if they can be bothered to remember that the TV won't power off if they've accidentally pressed the 'cable' button on the remote first)
HDMI helped a lot on the connectivity front, at least if you don't have any hardware older than a few years which lacks it, and sufficient inputs on your TV (you're just left with the problem of remember what is hooked up to HDMI 1, 2, 3 etc.) One never-used capability of HDMI is the CEC functionality that transmits remote control commands between pieces of equipment. It is almost certain Apple will make use of this to have the TV maintain complete control over everything plugged into it. How does it know how to control an arbitrary piece of equipment? There's an app for that! No app means no Apple TV owners buying your products, so the incentive will be there for makers of stuff like DVRs and Blu Ray players to create an app (more of a driver or interface definition file in this case, but they'll probably call it an app since "drivers" have scary connotations for people who have used Windows)
With the Apple TV controlling your Blu Ray player and cable box/DVR (it probably won't mess with your PS3 or XBox much, other than turn it on/off, while automatically selecting the appropriate HDMI input when turned on) they can put any pretty Apple like interface they want to paper over the shitty broken interfaces most of those products have. Imagine a Tivo you can talk to and say "record all new episodes of 30 Rock". Or even better, "next time that episode of 30 Rock that was on two weeks ago Thursday that I forgot to record re-airs, record it" (try that with a Tivo!) Of course this would be Tivo without the monthly fee! Apple could make every crappy cableco DVR a Tivo by having iCloud intelligence help it decide what to record in much the same way Tivo does (hopefully doing it better, otherwise I'll turn that crap like I do on my Tivo, but I know some people really this feature of Tivo)
Or they could and likely would go much further, securing deals with the major US networks and cable companies allowing them to "record" anything you already have access to. By recording I mean updating a few bytes in your iTunes TV profile out on iCloud saying that you recorded that program, not actually recording it since your TV would have no local storage....and you may just have a regular cable box rather than a DVR. You'd have it recorded even if your power was out at the time or it was repeatedly preempted by hours of afternoon weather updates about tornado warnings (those in the US midwest know what I'm talking about) Then you could watch it by streaming a pristine copy off iCloud, presumably even from your iPad when you are not at home (though that may be something even Steve Jobs couldn't negotiate) It makes sense, there's no reason why everyone needs their own hard drive with a separate copy of a program. If you could have recorded it, let's just take it as read that you did so but instead link you to acopy of the recording stored in the cloud. One which could, given suitable arrangements between Apple, the networks and their advertisers, potentially show ads more relevant to you rather than whatever was broadcast at the time. So old people won't see ads for diapers, and college students won't see ads for arthitis medications. In order to be saleable it would allow skipping ads as normal, but since studies show only half the people skip ads on DVRs now, this wouldn't be a big deal. And there's always the theory that people are less likely to skip ads that may be more relevant to them.
If we get something like this, it'll be US only at first just like iPhone was, and Apple would count on customer demand to get them the appropriate deals with networks in other countries just like how they bent over the cellular companies in Europe after doing so with AT&T in the US first.