None of the reports that we have received includes a "smoking gun", however at least one customer has seen his AppleCare MacBook replacement order stalled until Nov 1st, and another has seen pressure from Apple's financial department to make their purchase by today.
In addition, supplies of the current Core Duo MacBooks appear to be running thin. Earlier in the month it seemed as though Apple had achieved a supply/demand balance of the hot selling notebook. While the U.S. Apple Store still shows a turnaround of 24 hours for each current model as of this writing, some European online stores are beginning to have shipping times slip to 3 days for one or more model.
AppleInsider has previously stated that the Core 2 Duo revision was complete and a release was expected before the holiday season officially starts at the end of November.