Actually (now that Bullet is out) my current focus is on PhysX 3.2 and Havok 2011.3.0. Because of the huge changes in the PhysX API with 3.x it won’t be an upgrade, but a complete rewrite from scratch.
I am currently playing around with different ways to integrate, utilising the lessons learned with Bullet and trying out other, new concepts. The bad news is that it will be quite some time (half a year?) before any code will be moved into the Panda3D SDK builds.
As far as I know it is possible to build using the 2.8.4.6 SDK. This is the only version I have found in my archives, and I used this version when I did compile Panda3D with PhysX the last time.