Yep, I wrote this article 
As I see the cause: AAA games/developers are mostly oriented on console market, and Havok was always well optimized for consoles (for example, in Ageia times PhysX SDK for consoles was in pretty bad shape), so it simply seized top league without much resistance. Considering that Havok Physics is constantly evolving (with bigger development team behind it than PhysX), developing new products (Animation, AI, Script, etc), it is holding leading position in that area.
Also, AAA companies have money and resources that can be spend on better physics optimizations and bug-fixing. That also makes Havok physics look more stable and accurate in games.
At the same time, PhysX SDK has the best price/features ratio. That’s why it is preferred by middleware companies and mid-range developers. By the raw number of released commercial games (~ 550 currently) it wins over Havok.
PhysX 3 release was able not only hold current positions, but also win some new AAA integrations (Sony Online with ForgeLight engine, Square Enix with Luminous engine), however overall picture has not changed much.