Hey JB,
I'm not sure, but I believe you'll have to wait a bit before this happens..
Fred have to implement more of the Ogre engine into PB before he starts working on collisions (and physics?)...
AFAIK, the Ogre team does not want to incorporate collisions and physics to their engine, because there are a lot of good ones out there (like ODE?)
So, my guess would be that Fred first make the Ogre implementation more mature, before he starts to introduce collisions etc...
(I'm not sure if he's going to use ODE or some other engine, as making his own engine for PB would be a HUGE task..)
Now, I don't have any inside information or anything, but I wouldn't hold my breath too much for the 3D library to mature to a "usable" level before version 4...
Anyone with other information and/or other views, may start flaming me now!!
-Lars