Longhorn, your research is generally quite good, but there are a couple of facts amiss here.
Cable will most definitely have limits on their bandwidth. With simulcasting, they'll be able to provide the legacy analog beside all digital and have bandwidth for between 30-45 HD channels before a system upgrade is necessary. This was stated in a response to an analyst question during the CC last week.
Switched video has limits to only how many channels their encoders can handle so I have no idea what you read because they must have been talking about something else.
No such thing in the cable world unless you're the only one on the line from the head end to your house
Are you confusing this with VDSL2, which is a telco product and has a 1000 ft. limitation? Any cable solution is a shared line. Even if it were a gigabit uplink, you're talking one line from the head end to each 10 homes and even that is simplistic and doesn't account for overhead. And the more users you through at that during heavy load periods, the more your speed goes down.
The cap for HSI on the current Comcast system is generally thought to be in the low teens with all the other services they are rolling out being considered. That would apply to newer build areas(including my own, thankfully) where loads are not saturating the network.