I get your point and I do think that there should be some respect for Florida before even looking at the roster.
But what you said isn't impossible. Best recent comparable is probably Washington & New Jersey from 16 to 17. Caps won the Presidents Trophy with 118 points, then lost Williams, Johansson, Schmidt and Alzner and dropped 13 points in the standings. NJ was bad, then jumped from 70 to 97, closing the gap by 40 points.
Now consider this, the Caps had such a dominant team that they won the presidents trophy basically sleepwalking. So some of their top guys even had room to take it to the next level. Kuznetsov exploded (59->83), Ovechkin bounced back from arguably his worst season ever and won the Rocket and Carlson had a career season as their #1 defenseman. Their depth had some decent stuff as well (Wilson started scoring, Vrana & Stephenson rookie years), and in the end, the Capitals lost pretty much nothing up front. They actually ended up scoring only 4 goals less than the previous year.
New Jersey was a team nobody thought was any good. 18 yr old Hischier was their top center. No number 1 defenseman to speak of and generally a weak top 4. They had a great start and then played like a 85 point team the rest of the way with Taylor Hall putting up an MVP year.
NJ is proof that these teams can sometimes make the jump, and I don't think there's any question Ottawa looks like a better team. WSH is proof that PT winners can dip significantly even when players internally are able to make up for their off-season losses.
Difference between Florida and Washington is that Florida is going to have a tougher time making up for losses internally. Weegar is irreplaceable. No 3rd liner is going to put up close to PPG like Marchment. Duclair scored 30 and they can't even activate him from the LTIR. Tkachuk and Reinhart just had career years. White, Balcers and Cousins are the Wilsons, Vranas and Stephensons but are they as good even when these guys hadn't fully broken out? Meh. Barkov and Ekblad missed a bit of time so there's something if they can play all 82, but they haven't played a full season in 3 years so I'm not holding my breath. They also have the minimum roster which puts the team at risk for going in shorthanded occasionally if someone misses a game on a short notice. You can say the Panthers want to be better defensively under Maurice, but the Caps coach was Barry Trotz for f***s sake. Ottawa also has potential for TDL moves if they're in a good spot for the last stretch run, while the Panthers don't have much ammunition left.
So if we compare this to WSH/NJ, I can see a scenario for a 50 point swing, even if it's not the likely outcome. Florida has a very bright future still I think, but this is not the season to be cocky and have blind belief based on what they've done or what history says. It's going to take a solid season of hockey to make the playoffs, and as we all know, sometimes teams can have seasons where things just don't your way. Florida doesn't have the luxury anymore to take things for granted. If they can solve the current cap issues that would help, but there doesn't seem to be an easy fix that doesn't hurt the team further.
And as a sidenote; I don't know if the Senators are going to be a playoff team or not. Probably not is my guess. But the point is that can't be blind to different possibilities.