It seems to be a pretty widespread and credible rumour.
I don't agree with speculation that the reason for this is "so that Nikon can get into the mirrorless market".  They don't need Samsung for this, they made the 1 series with very fast on-sensor PDAF focusing years ago, if they wanted to bring that tech into larger APS-C/FX format sensors, then it would have been trivial to upsize the concept.
I suspect the reason is that it takes one competitor - even if very small - out of the market, but more importantly, it gives Nikon an opportunity to work with Samsung on cellphone cameras which have decimated the compact camera market, to mutual benefit.  I expect we'll see Samsung phones/phablets sporting Nikon or Nikkor logos before too long.