Considering we know the Model 3, which is to be denoted with the stylized "≡", will be a sedan – though perhaps with a hatch à la Model S, rather than a traditional trunk – and that there will be also be a crossover built on this smaller, more affordable platform, it seems quite probable it will be called the Model Y (which Tesla has already trademarked). It also seems likely it will also feature the somewhat controversial "falcon wing" rear passenger doors.
Now, as we mentioned, Musk deleted this tweet. This could mean that he misspoke or, more likely, that he revealed something he wasn't supposed to quite yet. It does seem to confirm, though, that the Tesla lineup will consist of Models S,≡,X,Y, and Roadster, remaining true to the company's propensity for humorous touches, like a stereo volume that goes to 11, "Ludicrous" mode, and the new "Bioweapon Defense Mode" in the Model X.
It wasn't the only Tweet he deleted from that session either. Another one, in response to to a question about a future Model X with a smaller, less expensive 70-kWh battery, elicited the response, "something like a 70, but probably around 12 months from now," indicating that there will be a less-expensive Model X option in the future.
Tweets that remain from the afternoon social-media frenzy? One that claims the falcon wing doors can act as an umbrella and that parts of the interior have a hydrophobic coating. Also, contrary to a (now magically-corrected) Google error, his height is not five-foot-ten, but, rather, six-foot-two.