  After a brief review of the present status of nonextensive statistical
mechanics, we present a conjectural scenario where mixing (characterized by the
entropic index $q_{mix} \le 1$) and equilibration (characterized by the
entropic index $q_{eq} \ge 1$) play central and inter-related roles, and appear
to determine {\it a priori} the values of the relevant indices of the
formalism. Boltzmann-Gibbs statistical mechanics is recovered as the
$q_{mix}=q_{eq}=1$ particular case.
