According to 9to5 Mac, retail copies of iWork '09 are running low at Apple Retail Stores. As one Apple retail employee told 9to5, "There is no iWork on the shelves, no iWork in stock and none on the way." That alone is a pretty good sign Apple's office suite is about to be updated, but there's even more. As you can see from the image to the right, type in "iWork" in the search field on Apple.com and the site will autocomplete "iWork '11." Signs really don't get clearer than that.
So why January 6th? Because that's the official launch date of the Mac App Store and it's unlikely that Apple would launch a Mac App Store without having a few new, shiny Apple-branded apps that appeal to a lot of people to kick things off. Plus ever since Apple previewed the Mac App Store back in October, the iWork apps have featured in all the official mock-ups of the store front.
iWork '09, the latest version of the software suite, was released on January 6, 2009. Nice coincidence, huh?