The ‘Tesla economist’ who I believe is an excellent follow believes for a variety of sound reasons that the plaid S HAS the 4680’s. As you said; time will tell.
I do agree with him that 1) due to the proximity to the Kato Road facility…2) the delayed release of the plaid S, and 3)…the complication of building the model S with a different battery and then having to convert the whole line to later accept the 4680 would not fit the Tesla business model that we have come to know and love.
I'm not convinced certainly; but I know some have ruled it out; and I think this may be a fools errand.