said by quetwo:I know all of that...
With modern cable systems, this is no longer the case. This is all just a matter of bandwidth. 4k signal takes 1 QAM with minimal compression running at MPEG-4. 8k signal will take 2-3 QAM channels each @ 6Mhz. (You can get about 3 - 5 720p channels into a single QAM, and about 2 1080p in a single QAM with minimal compression).
Modern 1Ghz systems (which, not all systems are at -- many are currently at 800Mhz or 550Mhz) can have ~ 157 QAM channels, although you wouldn't usually wouldn't have that many.
When you account for technologies like SDV (which is already out), you gain even more bandwidth in the final mile. There will be even newer technologies that come out soon that will allow even more bandwidth in the final mile by the time this hits the main-stream.