Down the line when it gets to the point that it's purely IP based, even from the LNB (or switch in the case of an MDU), what kind of bandwidth requirements and wiring requirements do you foresee? I'm guessing to guarantee QoS, the number of tuners supported would be determined by (speed of link)/(maximum theoretical channel bitrate)? Is there any idea at this point what that would be? IE: how many tuners would they be willing to install on a dedicated (no other traffic) 100Mb wired network?
Well, that all depends on the usable bit rate of a transponder. That in turn depends on what modulation scheme it uses and the amount of error correction ratio. Both of those could be adjusted over time, but let's make a WAG of somewhere between 1 and 2 Mbits per MHz. Maybe someone knows the real answer here?
If you have 12 500 MHz bands (they aren't all full, and not all transponders are fully utilized, but let's say they are) then that's 6000 MHz, or between 6 and 12 Gbps for everything, though of course even in the largest MDU not even close to all channels would ever be watched at the same time (unless the residents got together and tried a "flush all toilets at the same time" type of experiment on Directv ) Thus the output of all watched channels could easily be carried on a single cat6a cable running 10Gb ethernet.
Whether that 10Gb ethernet connection is available on a DSWM LNB or only on a DSWM switch, the MDU should need only the one. The DSWM would send the content via multicast so it would only require one copy of each watched channel, whether only one person is watching it or 100. Between that, and QoS, it is not a difficult problem network wise. These are both fairly mature technologies. The network cabling is no different than what a large MDU that provides ethernet to everyone would already have, or at least would certainly have by the time this was available.
In a home, you'd really need to have gigabit ethernet (which runs fine over ordinary cat5) as 100Mb would probably not hold enough channels for much more than a Genie's worth of tuners. Gigabit ethernet is super cheap now, and it will be impossible to find anything slower by the time you could get an IP DSWM LNB for the home. You'd be able to use wireless if you want, as that is already capable of speeds far in excess of 100 Mb, and even faster will be available in the future.