The Collaborative International Dictionary of English v.0.48:

pan out \pan` out"\ (p[a^]n`out"),
   1. v. i. To succeed; as, the project didn't pan out.
      [PJC]

   2. To turn out (profitably or unprofitably); to result; to
      develop; as, the investigation, or the speculation, panned
      out poorly. [Slang, U. S.]
      [1913 Webster]

WordNet (r) 3.0 (2006):

pan out
    v 1: be a success; "The idea panned out"
    2: wash dirt in a pan to separate out the precious minerals
       [syn: pan, pan out, pan off]