This sounds a lot like what Oiler fans do with their prospects. I still remember Oiler fans touting advanced stats that projected Denis Grebeshkov to be the next Scott Neidermyer. In reality Pastrnak is a winger in a system that isn't conducive to winger bottom lines. 60 points is the normal top end for a legitimate first line winger in Julien's systems. That isn't to say Julien's system isn't conducive to offensive production on the whole, just the opposite, but it relies on more balanced scoring across the board and wingers, especially top 6 wingers ice time and production does suffer a bit.
Boston hasn't had a 70 point winger in Julien's tenure (I don't believe) and I don't ever see that changing. Their ice time is limited to the point where it's limiting to their individual numbers. When most leave they notice a rather immediate uptick in bottom line season totals. This was true for Seguin, Kessel, Wheeler, and even Ryder.
If Pastrnak can eventually become a 60 point winger in this system, that will be a huge win.