Weirdly, some form of Articulation Element Modeling (also known as Super Articulation 2) was included in the NSX-1, the chip embedded in the NSX-39 Pocket MIKU. Technically, there is some conceptual (mathematical, algorithmic) connection to Vocaloid.
The SA2 Female Vocals expansion pack played with this idea in the opposite direction -- bringing Vocaloid-like synthesis to SA2. Like many technologies, Yamaha experimented, tried it out and then abandoned.
Technically, SA2 synthesis is very much possible in the existing hardware. The trick is convincing Yamaha marketing otherwise. Plus, there are front panel controls, further software integration costs to consider.
I agree with Mark. I don't think Yamaha will give up on this top-of-the-line differentiator.
Always willing to be shocked and surprised -- pj