I will say right now though they won't get that 3rd in a row.
IMO there are only two things that can prevent them from going back to the finals a fourth straight time.
First, age might catch up to Bob, he'll be 38 at the start of next season, as we all know father time is undefeated and at some point Bob will eventually slow down. That said, the guy keeps himself in great shape, and according to his teammates he's the hardest worker on the team. They just won the Cup without having home ice in any series, so the team knows the regular season isn't as important to them as it is to other teams, I'm sure the coaching staff will give Bob plenty of rest during the season getting ready for the postseason grind.
Second, the wear and tear of going to three straight finals might catch up to them physically and mentally. In reaching three straight finals they've basically played four seasons worth of games in just three years, that's a lot of hockey, and there's a chance they just hit a collective wall at some point in the playoffs. I remember when the Heat went to their fourth straight finals, LeBron made a comment that during the series against the Spurs, the team just hit a wall, playing so many games during that four year span they had nothing left physically and mentally, and the Spurs beat them rather easily. The Bills went to four straight SB's, and I remember an interview with Bills receiver Don Beebe, he said at halftime of their fourth SB against Dallas, he recalled looking at his teammates in the locker room, and he could tell by their body language they had nothing left in their tank, he said the emotional, physical, and mental toll hit them at halftime, they got blown out in the second half. I've always remembered the comments made by LeBron and Beebe about what a toll going to that many finals in a row takes on an athlete. So there's a chance that playing four seasons of games in three years catches up to them.
I'm not saying this because I'm a fan, but I truly think this Panthers team is special, they're as talented as any team in the league, deeper than most, extremely well coached, they have no weakness. In the last few days I've heard analysts debate whether this team is the best team they've seen in the past 20-30 years, they're that good. We'll see what happens in the offseason, but until someone beats them four times, to me they're still the team to beat