The reality is, if Lomberg and Frk take their spot, they likely weren't ready anyways. Coronato likely takes Mangi's spot in the middle 6. That means Pelletier is competing with Frk, Lombo, Rooney, Duehr, Hunt, and Klapka. There is essentially 3 spots for those 7 people (that includes 13th forward). And that's not necessarily for a 4th line role, as Coronato (still competing but his spot to lose), Pospisil, and Zary are all flexible between 2nd and 4th lines, so if Pelletier makes it, it could be anywhere on those three lines.
I'm looking at it as:
Huberdeau-Sharangovich-Mantha (Mantha being pump-and-trade, opening up another spot later)
Zary-Kadri-Kuzmenko
Coleman-Backlund-Coronato
Lomberg-Pospisil-x
x
Those x's are the biggest wildcards, but that doesn't mean that Coronato doesn't get sent down if he doesn't outperform. And with Mantha almost certainly getting traded, and potentially Kuzmenko, there's almost certainly incentive to be the guy (whether it's Coronato, Pelletier) to step up and be put in a top scoring role. It's also why someone like Zary and Pospisil are so flexible in this lineup, as wing or center, and anywhere from 2nd to 4th line.