I hope this brings closure to Computer Scientists. But you folks do realize that if P != NP then there is a God, If P = NP then there isn't. In other words, you can't have infinite "free efficiency". If you can do an infinitely complex task in reasonably efficient time then you can hack reality and get to God. God made P != NP so that we're locked in our own universe.
No. Bullet Physics and OpenCL is the answer to this problem. Not a closed standard like DirectCompute that you can only use on Windows. Havok will use Larrabee, PhysX uses CUDA, however they will all eventually use OpenCL eventually. Although Bullet Physics can be ported to Larrabee, CUDA (already demos exists), support for OpenCL is the right way to go.