Based on the recent history of the league, "He's (age) and making (dollar figure) for (number of years)!!!!!" does not appear to be as compelling an argument to NHL GMs as it is to us on forums.
Petry will move in the offseason for a solid return. Time and time again on HFBoards we treat players like they're completely done and dusted after their first setback, and assume that NHL GMs as a monolith think the same way, and almost every time this happens the "unmoveable" contracts end up moving. It really isn't that hard if you're willing to take back another team's bad money which we absolutely will and should be doing. A team with no guarantee of being in the playoffs paid a 1st for Rasmus Ristolainen this offseason.
It only takes one GM for a deal to get done here. It is not going to be hard to sell teams on the idea that being away from his family and recovering from injuries after a short offseason and losing all the leadership on the team was the primary cause for his difficulties and point out that the tools (and especially the skating) are all still there. Every team has bad contracts, if we're taking back 3 or 4 million from someone else it's certainly feasible to get another team to dream on what Petry could be for only 2-3M of marginal cost to their team.