As soon as the iPod touch came out (maybe even before that), Apple immediately ended any new iPod games for clickwheel ipods. I know, it's not technically the same, but close.
BUT, you could still buy a clickwheel iPod and buy the current games before the Touch announcement and still play those same games after (and I belive still purchase games for the clickwheel iPod too...you just weren't getting new ones)...
And the worry was that the ATVs out there would not function when the new version was released which is not true. I mean, even if for some strange reason they completely change movie delivery methods to alienate the current ATV you would still certainly be able to play back all of your current iTunes items. (BTW, if they did change that method, it would likely affect iTunes as well and lead to a new version release which might also eliminate hundreds of thousands of other folks' ability to rent or buy movies and songs...meaning less money for Apple.)
Heck, I can guarantee that there are still people using Mac Classic computers out there for some tasks and they are performing as well as they did when the machines were new....even though Apple may no longer support those systems.
Yes, things can change...with Google YouTube delivery methods being the biggest question mark...but all in all the current AppleTV could function for several years. Chances are if you bought today, you'd probably get a new one in a few years anyway.
I also do agree that current aTV's will still be supported, but don't look for any new features to pop up.
Which is exactly what I was saying.