Al, I don't think anyone thinks it will be a new S camera, only perhaps a miniaturization of one, which incorporates some of the technologies like the Maestro processor and AF technology...more of a mirrorless R....
I agree with you that their decision to stick to 37.5mp in the S puts them in somewhat of a bind with respect to resolution. No matter how much the execs say 37.5mp is "enough" for everyone, there is only so long that they will be able to do so. As 40-50mp becomes the norm for the high resolution 35mm cameras, getting someone to pay 13,000 US extra for a lower resolution camera with similar or lesser high ISO performance will be quite a hard sell. Even harder than it is now...and I say this as an S user who also uses the A7rII. The S (006) still has the quality (by a hair) and handling edge, but it is too close for comfort. As for why they chose to keep it at 37.5mp, personally I think they pay too much attention to fashion photographers, because that fits their idealized image of their camera system. Since they rarely need larger than a magazine spread, they are more interested in frames per second, live view and the ability to do some in camera video. They also thought, probably correctly, that many people don't print very large, and that 37.5mp is more than enough for most purposes. While rational, it disregards human behavior when it comes to these types of purchase, which is a desire to be ahead of the competition. People buying a Ferrari like to know that it is faster than their neighbor's Subaru, even if sometimes it isn't, as in the case of a WRX STi.
In reality, most users of the S are wealthy amateurs or working pros with extra income to spend on a high quality system that will handle all conditions and features the best possible lenses. Certainly a balance of speed (both handling and ISO) is important, but they cannot do so at the expense of sacrificing their image quality and resolution advantage. The fact is that they released the S at 37.5mp when the highest resolution 35mm cameras were 24mp...that was already six years ago and the resolution is the same, as is the overall image quality at moderate ISOs. At the time they billed their lenses as being capable to survive the next three generations of pixel sizes, such that they could tolerate sensors with up to 100mp...hopefully they will design a body to suit those lenses! Increasingly even people who are invested in the system will ask themselves, "what's the point in spending 8000 USD on a lens and 16,000 on a camera body when you can buy a 3000 dollar camera with a 800 dollar lens that out-resolves it?"