Analysis of information sources in references of the Wikipedia article "Source" in Danish language version.
Since they licensed and integrated it into Source, Valve have been tweaking and adding to Havok to the point it's virtually a new animal. Almost every aspect of the Source engine follows on from the physics — including the sound, graphics, AI and animation. When asked whether or not they would be upgrading to Havok 2, Valve seemed to suggest they probably wouldn't, in part because H2 wouldn't be much of a step forward from what they currently have.
Since they licensed and integrated it into Source, Valve have been tweaking and adding to Havok to the point it's virtually a new animal. Almost every aspect of the Source engine follows on from the physics — including the sound, graphics, AI and animation. When asked whether or not they would be upgrading to Havok 2, Valve seemed to suggest they probably wouldn't, in part because H2 wouldn't be much of a step forward from what they currently have.