Well, here is what the press release says, verbatim. It addresses your concerns, and there is no indication that it will not apply to all cars (obviously the announced Auto Pilot features only apply to the newer cars):
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Valet Mode
Valet Mode conveniently and discreetly limits Model S’s driving performance and restricts access to certain settings and personal information. With the touch of a button, owners can place a limit on speed, lock the glove box and frunk, and disable personal information like driver profiles and homelink settings.