What this means is that you should expect an increase in the number of search queries in your analytics data showing the always fun [not provided] response.
Like I said before, what this means for SEOs and webmasters, as well as marketers, is that the "Not Provided" in your analytics "keyword" reports will just increase. Right now, I am at about 30% of all my keyword data says "not provided." I wouldn't be surprised if that jumps to 40 or 50% once this is rolled out.
Danny Sullivan gets into some of the loopholes with this.
But do expect your not provided keywords to spike up as users upgrade to the latest version of Firefox.
Forum discussion at WebmasterWorld.