I'm assuming that trading Petry will require us to take salary back in return, not that it's a problem in our current situation.
Contending teams probably wouldn't be interested in Petry at full price, so it'd probably be a rebuilding team that is looking for useful vets. Detroit might fit the bill.
Another two teams that might fit the bill: Philthydelphia and Ottawa.
For Philly: A trade built around Petry for JVR to make the salaries work. Use JVR hard for a year, trade him at the deadline with salary retention.
For Ottawa: A trade built around Petry for Hamonic to make the salaries work. I do think that a pairing for Chabot - Petry is legitimately very good, assuming Petry returns to form.
For Detroit: While Detroit doesn't have cap issues, they're going to need to sign some players & give Larkin a raise. Maybe something built around Alex Nedeljkovic
If Pittsburgh can't re-sign Letang, that might be a logical landing spot for them.
If I had to bet money for his most likely landing spot? I think it's Philly. Fletcher needs to win and win soon, or he's going be short a head.