Upload & Sell: Off
I have serious S system envy, but the cost is prohibitive.
The prices of the S lenses, especially if you buy used, aren't too dissimilar from other top-of-the-line MF glass, like Phase's SK leaf shutter line. There are two recent eBay transactions where a 70mm went for around ~2200 and a 120 macro for ~3500 or so. The lenses are built so well, there is no reason to ever buy them new, unless you're a collector and want them nice and shiny.
What is overpriced is the camera body itself, which is by no means a modern design on paper, though the camera is a joy to use in practice. From the two times I shot with the S (never used the S2), it felt astoundingly intuitive, here was a camera I've only seen in a few pics online and I can already make sense of it's operation without a manual. It could have been the ideal camera if it used 2013-14 technology and was a bit cheaper.
$23k for the S2 was just too much, and $21k for the S is still a lot of money, but if Leica continue this trend and makes a 50mp CMOS S for around $19k tops, it would be a much more reasonable option. Unlike four years ago, you can actually find lenses for the system, and they range all the way from 24-180mm, meaning you can actually buy into a system now. The lenses are perfect, the ergonomics and design is perfect, now all Leica needs to do is make the camera technologically competent and price it more in line with it's feature set.
The Pentax 645DII is certain to be $10k, Hasselblad is at $27.5k and Phase One at $35k for the back only; with this kind of lineup it makes sense for Leica to fit somewhere in-between the Pentax and Hass in the price spectrum, about the $19k I predict the CMOS S to be. This trend isn't going to change unless someone, like Sony, comes out with a really "disruptive" camera, like an up-scaled a7R as some people talk about here. However this is not especially likely in this hardware generation, because Sony only just launched a new camera system (the a7 series), and they probably won't be thinking of pushing the limits more than they already have.
I just want to make the distinction that while the next S will be cost-prohibitive for most people, it won't necessarily be overpriced in the grand scheme of things, not as much as the S2 used to be.