The teaser webpage this appears on has the world "final" in the URL. The text says, "Next time, a new Evangelion movie :||" (次回は シン・エヴァンゲリオン劇場版:||).
What the hell is :||, you might be asking! It's a repeat sign in music; but if it's just two lines (as commenter Zer0Cal0ries points out, a "double bar"), then it means the piece of music ends—and it's unclear whether that is a colon and then two lines (a double bar) or just a repeat sign (man, my head hurts). The problem is that if this is actually used in the title, the general public won't know how to say it or what it means. What we do know is that "Evangelion, colon, vertical line and darker vertical line" doesn't sound very cool.
This symbol does make sense because the naming of the recent Eva films, as goofy and pretentious as they are, appear to be based on the traditional three act structure in Japan of jo-ha-kyuu (序破急), which is often translated to "beginning, break, rapid". This structure is common in Japanese arts.
This structure seems to exist in the new Evangelion movies, which are called Rebuild of Evangelion (or Evangelion: the New Movies) in Japan. In the original Japanese title for Evangelion 1.0, there is a "jo" (序). Before Evangelion 2.0, there is a "ha" (破). However, before the recently released Evangelion 3.0, there is the English letter "Q", a pun for "kyuu" (急).
Those who know Japanese will noticed that the Rebuild of Evangelion movies write Evangelion (ヱヴァンゲリヲン) slightly different from the way the series was traditional written in Japanese (エヴァンゲリオン), as a way to mark a distinction—highlight the "rebuild" quality, if you will.
Also, "new" (シン or "shin") is written in Japanese katakana for the just announced Eva as opposed to using the kanji character (新). However, this is assuming "shin" here actually means "new". Since it's being written phonetically, it could stand for, for example, the "shin" (真) kanji character that means "true", "real", or "genuine".
That musical symbol, then, would infer that this is not only an end to the Rebuild trilogy, but a return to the roots of Evangelion—another reboot? Or it could simply be "Evangelion, colon, vertical line and darker vertical line."
In case you missed it, here's Kotaku's review of Evangelion 3.0.
次回 シン・エヴァンゲリオン劇場版 [Teaser Site]