This ignited a debate over at the Tesla Motors Club and user Adelman has now posted a picture that a friend took of a Model S with P85D branding [UPDATE: Image removed from this post, but you can see it here]. This doesn't help us know exactly what we're looking at, but it does make the picture a bit clearer, since we can eliminate the idea that there's a Tesla Model D coming. And things come even more into focus when we put Musk's Tweet into context with not only previous company statements about an all-wheel drive Model S based on work being done on the AWD-only Model X but also a new Tweet by Edmunds' Mike Magrath that says, "According to the guide there's supposed to be an all-wheel drive Tesla here at the Paris Motor Show. There is not." See the Tweet and pic below.
Given these pieces, it's looking pretty clear that the "D" Musk mentioned will be the AWD Model S. Now, about the "something else" he hinted at. What could that be?