The information comes from a user of the Apple discussion forum who would have received an iPhone 3G 8Gb but with iPhone 3GS 8Gb packaging. If the information is correct, it would be an error by Apple which would indicate the imminent marketing of an iPhone 3GS 8Gb including the occasion of the Apple Special Event in January. As a reminder, even if there is no longer any real doubt that there will indeed be a Special Event in January, it has not yet been officially confirmed by Cupertino.
We discuss it on the forum.
[Via TouchMania Thanks Fred64 for the info]