Vegas is smart for not initially wanting to overpay him. I don't think he will repeat the 40 goal season. Probably around 20-25 goals is where he fits. He isn't worth $6.5m, $4.5m is fair for him.
That's quite a guess. Any NHL player would score 25 goals if centering last seasons Marchessault and Smith. Not to mention, in the whole NHL history, there has only been couple of cases with that kind of scoring slumps (and I don't remember either of them). 20 goals would mean a slump of -23 goals... He would practically have to lose half of his brains to manage to slump that hard.