If it was proven that it&#x27;s not in P then we would have shown that P!=NP which would be <i>HUGE</i>.<p>No, this is &quot;merely&quot; finding a more efficient algorithm for a problem which we still don&#x27;t know exactly where belongs. From a complexity theoretical viewpoint nothing is changed. It&#x27;s still possible that graph isomorphism is in P.<p>Now if graph isomorphism is shown to be NP-complete then this result would imply that every problem in NP can be solved in sub-exponential time which would have huge practical consequences.