I see the logic in your post, if it was just about assessing plausibility, I would simply agree your scenario is plausible.
But given your opinion is more dramatic than that, my opinion differs somewhat. IMO we can't jus dismiss the rumors of the refreshes that do exist, assuming we believe they are not fake rumors of course (it is possible they are fake, but IMO they seem plausible).
Model Y/Semi/Roadster seem far-enough away, and Model 3 ramp problematic-enough (especially margin-wise), that the viability of Model S/X would still quite potentially seem relevant in the next year or two.
If Tesla has worked on that like the rumors suggest, then they might well be close enough to release those changes even if the focus is shifting. Keeping Model S/X viable through 2018 and into 2019, IMO would benefit from upgrades hopefully sooner rather than later.
We shall see. I respect your opinion and speculation, it is helpful IMO.