Well, I certainly got a response. My criticisms were influenced by the probabilities of mass acceptance, rather than the undoubted abilities of luthiers.
Here's the original question:
"So, since technology has marched along nicely, I'm wondering if some lower note will become "mainstream" and at what point. For example, does anyone think the low F# (a fourth below the low B) will become commonplace and if so, how many years from now?"
My main point about the concept is not to deny that there will be persons who master the design, building, playing and reproducing of an F# string, but those myriads of others -- me, alas, among them -- who are not virtuosos nor moneyed amateurs.
After all, the option of an F# string is available now, if you can find the right builder, and it is certainly a good thing if you have the chops to exploit it, which includes a reasonably good transducer system.
But we're not talking (as I understand it) about What Would Jaco Do but, rather, general adoption of a new paradigm. I have nothing but respect for those who can exploit uncommon tools of expression, but the question was, when will a low F# string become "mainstream". That's a whole different issue from whether it can be done or whether it's desirable to do it, or whether any individual here has already done it; and that's the issue I was trying to address.
For you who are using such low tunings, I salute you. But you may want to think twice or maybe thrice before you claim that your particular facility is "mainstream."