Okay -_- I think you know very well when I say "source" I mean the source resolution of the playback format, not how the movie was originally filmed. Until a playback device is released that actually outputs a 2k, 3k, etc. picture you're not going to see much of a market in the U.S. for any sort of TV beyond 1080p HD. And that's years beyond the release of the Apple TV.
If anyone here thinks Apple is going to market a product meant for playback of resolutions beyond next Christmas you're more than drinking kool-aid, you're drinking kool-aid that's been spiked.
I think you're overly pessimistic about the advance of technology. As someone has already pointed out (
here is a ~$1k 4K upscaler) there are some 4K devices out there, including support in Ivy Bridge for 4K resolutions from the integrated GPU. Retina rumours and artwork for OS X are some more examples.
Lets not forget that Apple was among the first to introduce (and mass manufacture) the high DPI iPhone 4 screen.
If you consider how long TVs have been on 1080p (it's rather incredible really), then you can see there really is room for progress to be made. Apple has the clout, and the brand draw to drive up adoption of a technology that's not even out there yet, because they know it more or less will make a huge profit. Sounds like I'm on the Kool-aid too? Perhaps, but if you look at Apple's latest efforts, I don't think they can fail, as long as they price it right (and they've learned their lesson).
We have issues of distribution to overcome still, and that's the part that Apple has least control over, but I didn't say it was going to happen overnight. The London Olympics are being broadcast in 4Kx2K is very decent progress, and shows industry is pushing forward and Apple won't be a lone initial player.
Regarding streaming, well that's a hurdle that'll be overcome in time. We don't need much detail beyond 1080p in a living room setup, however for UI applications, higher resolutions would be a change you wish they'd brought up earlier. For example, reading web pages from the PS3 on my 46" 1080p TV at about 3-4m away, it's actually very uncomfortable to read the text, say on this forum or news sites.
So while the world's ISPs and media industry sort out 4K production and distribution, we can make do with Apps on your TV.
I can't wait.