If you're good this year, SEOers, Google will make sure there are no major changes to how websites are ranked, as the company has done in previous years, just before the Christmas holidays. But if you're bad, expect to be put in SEO Time Out by being busted 30 ranks.
Webmasters have often complained in the past that Google has updated its algorithm just before Christmas, knocking the mom-and-pop stores off the map for a while.
According to Matt Cutts, who's not making any promises, all should remain as it has been:
I know that webmasters are especially sensitive to quality/webspam/ranking changes in Q4 because of the holiday season.
If we've got something that evaluates well and that we think will improve quality, we can't just pause for 1/4th of the year, but if anything big launches I'll try to be available to answer questions and help get a handle on any changes.
(Right now I'm not expecting radical changes in webspam ranking, but I know better than to make a promise.)
However, if your site suddenly drops in rank by 30 places, then that's the equivalent of a lump of coal. In what the forums are calling the "place 31 phenomenon," it appears that Google is dropping sites by 30 spots for 30 days as a penalty for breaking the rules.
The speculation is that a sudden burst of links, or other SEO tactics on the black side of the hat, will put a webmaster in the penalty box until he or she fixes it.