Pure 2 has been cancelled by Disney Interactive Studios, who also published the first quad-bike trick racing game.
The original game was highly praised for its huge and pretty environments, its crazy tricks and its intuitive controls. Although some people said that the game lacked enough depth.
I imagine that a sequel would have been more of the same but on a grander scale and with possibly more vehicles added outside of just the ATVs. The sequel was never even formally announced and apparently was canned without a reason given.
Here is a video review of the first Pure which was released in September of 2008 for Xbox 360, PlayStation 3 and PC.