A new trailer for Skyfall was debuted at Comic Con according to a report published by CinemaBlend.com. The report gives a description of the trailer, which appears to add quite substantially to the teaser trailer released in May and includes footage of the train sequence shot in Turkey and other action shots. The trailer also appears to reveal what M’s problem is, as well as introducing Ben Whishaw as Q. The actor was finally confirmed by the producers as playing Q after months of denial, although much of it was half hearted.
CinemaBlend finishes by saying that the new trailer will be available online, although no timeline was given for that. Given its very public airing, I think we can expect it soon.