Nvidia will likely support GPU accelerated PhysX on consoles even if they use AMD GPUs, there is no practical reason not to. I imagine they will continue to keep it exclusive to their cards on PC tho sadly.
To my knowledge there still isn't a true competitor to PhysX yet, no one has built another physics engine that supports GPU accelerated, particle, cloth, rigid body, and fluid simulation.
Bullet only supports rigid/soft body physics as far as I know. And no game so far has used GPU accelerated Bullet Physics as far as I know ether.
And Intel cancelled the GPU accelerated version of Havok so that is not really an answer ether.
I wish there was a good OpenCL physics engine, but sadly I can't see any turning up any time soon.
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