It's not a 1 way street though. Regardless of the Canes salary structure, IMO, it's way more likely that Sekera didn't want to re-sign here in the first place, and I've felt that since day 1. I'm very confident that Francis and Peters definitely wanted him back given how weak the defense is without him. They would have had to vastly overpay him just to entice him to stay, and even then, that might not have swayed him.
Think about it. He wasn't drafted / developed by Carolina and had only played 1.5 seasons here so he has no real ties to the org., no roots. He's in his prime (29 when next season starts) and this is his best opportunity to cash in after a couple of very good seasons. The Canes likely won't be contenders for a number of years yet (and maybe not even then) and he's only been in 8 playoff games his whole career, etc... IMO, there was very little incentive for Sekera to re-sign here before seeing what is out there in UFA land and even then, I doubt he'd come back (maybe if he wins a cup and the Canes through gobs of money at him, but even that is unlikely).
I honestly don't think Ward's, or Semin's, or Khudobin's, or Staals' salaries had anything to do with it. If you were in Sekera's shoes, would you rather go sign with the Kings for a little less money and know you are going to be a contender for probably the rest of your prime (as well as playing with Gaborik), or take a little more money and play in Carolina who is likely rebuilding and won't likely be competitive for a number of years? I know what I'd do.