Theory (partially lifted from Elektrek): Model 3 has the new unified ventilation system in order to provide more room for the optics of a huge HUD projector Model 3 reveal part III was stated by Elon to be 2-4 months away - 2 months ago. Model 3 reveal PT III will show the "spaceship controls" that Elon tweeted months ago will be the steering and control system - unless there's a reveal PT IV - but we're awfully close to the start of production. Continuing Tesla's promise to put new tech in Model S first and also to avoid Osborning - HUD / spaceship controls come to Model S at the same time. Model 3 production still slated to be launched in second half 2017 and Musk still claiming 100K+ cars produced in 2017 - so I'd think the final dash design is locked or close to locked at this point - they could have been building/designing a similar dash for the S/X in parallel all this time. If the control system of the Model 3 is a radical departure from the prototype (Elon's own words "wait til you see the real steering and control system - it's like a spaceship") is it possible the Model S has an entirely new dash and interior waiting in the wings to be sprung on us any minute now? Counter argument would be that the Model X's interior is identical almost to the S and it was just introduced 12 months ago. If the HUD *does* show up with the existing dash - are we now going to have three separate displays on the S? Steering wheel display, center screen AND a huge HUD on the windshield?