My few cents:
The current SWiM doesn't share when two receivers are tuned to the same transponder.
The external SWiMs also have six inputs, so there is "some room" for more SATs.
I've been told current SWM shares channels by others on dbstalk, but I've never tested that, so I have no reason to doubt your statement. At any rate, there's nothing stopping the DSWM from assigning multiple receivers the same SWM channel, so long as the DSWM made the Directv channel each wants available on that SWM channel. If the SWM channel assignment to the receiver is fixed, then the DSWM would have to create its own SWM channels to do so. And it will (but not the DSWM13, see below)
I recently noticed Sonora had a new model of amplifier, which has 6 inputs/6 outputs like the model it is replacing, which I confess at the time made me wonder if Directv might have plans to use more inputs for RDBS, given that Sonora would undoubtedly be aware of Directv's future plans. Of course, Sonora might have left it there "just in case".
As for the DSWM, if the current thoughts hold true, it's an evolution of the current SWiM, "but" will have more of a receiver so it can decode "a channel" from the transponder. This will then be encoded [modulated] onto an RF signal and become "a SWiM channel".
Software in the receiver should be able to "fine tune" to these new frequencies, but "I doubt" we'll see 40 channels, if they're starting at 13, since this requires 13 tuners and encoders/modulators.
Well, unfortunately I have to eat my words about what I said before. I finally had time to sit down and read both patents in detail, instead of giving them a more cursory examination (i.e. skipping ahead to the end figuring that's where the good parts are) There are no tuners or modulators (even digital equivalents) in the DSWM13. The patents actually describe three (or four, depending on how you count them) embodients of a Digital SWM, which is why I should have read them in their entirety before commenting
The first is very likely what the DSWM13 is. While it is "digital" in terms of using ADCs to digitize the entire RF bandwidth being transmitted by Directv, it isn't performing any higher order digital operations. It fits 13(14) channels where 8(9) used to go, using an entire transponder at a time. Basically it uses smaller guard bands as has been previously suggested. This device is figure 4 & 5 from the patents. What I've seen elsewhere suggests it is also cheaper than current SWM due to the elimination of SAW filters.
Figures 4 & 6 is the second embodiment, which utilizes some higher order digital functions but still operates at the transponder level. Of note, it describes the choice of a 32 point FFT, despite a maximum [for SWM] of 26 channels, because powers of two simplify the FFT implementation. So we might reasonably expect a DSWM26 in the future utilizing the technology in Figure 6.
Figures 4 & 7 is the third embodiment, which is what I've been describing, but we may not see for a while. It operates not on transponders but on individual channels, computing I/Q data for each channel of interest. These can either be pasted together on the fly and converted back into analog SWM channels (with at least 100 HD channels possible from the 26 SWM channels) or can be sent via IP.
The patent actually lists several possibilities for this third embodiment, adding further processing of the I/Q data, to the point where it is fully demodulated. So we may have to wait until the 4th generation DSWM to get one that can work directly with RVU devices as I was suggesting. Though depending on how long it takes to get there, there may well be a competing protocol which Directv would use in preference to RVU.