Just read a Scientific American review of a recent article which suggests evidence for sterile neutrinos:
The article is a little unclear about exactly what evidence, but my question is more general. A sterile neutrino would certainly not necessarily imply a forth generation to the standard model - if memory serves there is some nice anomaly cancellation which would be ruined if we had four generations. I am mostly interested in what a sterile neutrinos would mean for supersymmetry - are they part of the MSSM? What is the minimal number of SUSY particles which must come along with such a neutrino? Do they HAVE to be SUSY, or can they be part of an extended SM?