The acquiring company will be either Newmont Goldcorp or Agnico (doubt Sean Boyd wants to start a catfight with Newmont).
I think part of the low price is liquidation of shares to put into 'sexier' plays, but as you said, this is a proven resource. PRB traded as high as 2.18, so there is undoubtedly some tax selling.
Groups/institutions holding large blocks of shares aren't going to give it away. I believe we'll see $5-6 /share, all stock offer.
Remember also, by the time this occurs, POG may be sitting around $1600-1900/oz.
WB