Just thought I add more fuel to the speculation fire. This has been circulating around on reddit. Apparently, this is the leaked audio for the upcoming teaser.
Of course, it's authenticity is still being questioned and debated, but it does follow a similar format used in the previous Fallout teasers (scrambled audio, licensed song transitioning to orchestral score, etc.). The orchestral piece itself is possibly original and sounds like a variation of the Fallout 3 theme.
If it turns out to be fake, it's pretty well done and it definitely sounds like something that would be in a typical Fallout teaser, but we'll see.