Top Gear will return in January 2012. There will also be a Christmas special for 2011.
There's a video, here, with Jeremy and James talking (mainly) about Top Gear Live, but they also mention the special and where it will be set, but I won't mention that in case you don't want a spoiler. They also mention the 18th series and some of the locations for filming.
Just to recap: if you watch the video you will learn the location of this year's special, so don't look if you want a Christmas surprise. And let's be honest: who doesn't want a surprise at Christmas?