Jonno said:
If it hadn't already been strenuously denied that he'd be involved, I'd swear the music in this trailer is a Michael Giacchino arrangement of the Williams themes. The rising scale is very much his style.
He wasn't involved. Some sources say Williams recorded the music within the last week or so. It has been confirmed that composer Felix Erskine contributed to the teaser music, but to what extent, we don't know. It's speculated that all the orchestral material is done by Williams and Erskine simply "beefed" up the music to make it more trailer-like. Erskine is being vague (possibly intentional) as to his contribution.