If Lombardi trades Carter, he's making a big mistake, IMO. Take him away and teams can focus on shutting down Toffoli. Dowd has been good, but thinking that, after only 11 games, he's ready to jump up and permanently replace Carter as #2C and keep Toffoli productive, a player whom he's never really played with, would be completely rash. LA can't afford to trade a veteran scoring forward and leader like that right now, not with the forward cupboard so bare of talent. They'd probably get a forward back, but he likely wouldn't be that good, since Halak's and Carter's caps almost cancel out, so the forward would probably be a cheap throw-in, more or less.
If I were Kings GM, I'd make Muzzin available. He's not as good as people think that he is and, therefore, his value as a trade piece is higher than it should be. He's coveted around the league, he has a $4M cap hit and he's been awful this season. That's the perfect place to start rebuilding the team. I know that the Islanders need scoring, but he's an offensive defenseman, so, perhaps, there'd be interest. If not, then there are other teams. LA would still have Martinez, who's a similar type of defenseman, more dependable, has been around longer and tends to come up bigger.
I also wonder if the Islanders would be interested in Purcell. I know that he's gotten in only 3 games, but I didn't understand why Lombardi signed him in the first place. He just wasn't made for the Western Conference, it seems. In fact, he'd played only 2 games before he became too "banged up" to play for 2 weeks. He could be better back in the East, perhaps playing alongside Tavares, in the same way that he had his best seasons alongside Stamkos, I believe. If the Islanders believe so, too, they might give something decent for him. Lombardi probably won't give up on him this early, though.