Although there is still hope for a holiday's release, Shacknews got this confirmation from one of Valve's team members that the awaited Half-Life sequel won't be making it into the stores September 30th as was previously announced:

The previously announced September 30th release date for Half-Life 2 is being pushed back. We are currently targeting a holiday release, but do not have a specific "in-store" date to share at this time. We will release that information as soon as we have confirmed a new date.