Was it the end for Chicago, when after winning the Cup in 2010, they had consecutive first round losses in 2011 and 2012?
Was it the end for Pitsburgh, when they made it past the second round only once in the six seasons after their 2009 win, including a rather decisive beat-down by the Rangers in 2015?
Colorado still has a high-end team with elite-players. They didn't exactly lose againt rabble either, a six game series against the top team the western conference is nothing to sneeze at. They have all the means to get themselves back on track. It's a 32 team league now, even great teams will have a tough time making it to the third or fourth round now and then. Sometimes you just have the misfortune of running one another great team rather early on. Imagine what would have happened if Colorado, Detroit or Dallas gave up, just becaues they ran into each other quite often in the late 90s / early 00s.
Kane and Toews were in their early 20's in 2010. When Pittsburgh finally won again in 2016, Crosby and Malkin were basically as old as MacKinnon is now. Not that that guarantees anything one way or another, but Chi and Pit may have had a little more time to "re-tool" the roster. And time goes by quickly. Makar is a UFA in 3 years, Rantanen a UFA next summer, and MacKinnon will be 29 in Sept. That's not Chicago in 2010.
Once you lose your depth for cap reasons, and your top guys get their Cup contracts, and now it's been 2 years since you won the Cup, it just gets more difficult climbing back up the mountain. It'll be another year grind just to get back to the end of the 2nd rd. Same thing with TB. 2 years removed from a Finals appearance, but 3 years removed from the Cup win, and it's not getting better. Everyone is close to, if not 30 already. Everybody got paid. Stamkos is a UFA and will be 35 next year.
The Avs won't go away. Too much talent to do that. But, windows, if you want to call it that, usually end before you think they will. Once you start not winning the Cup, it's a little easier for seasons to go by. Eh, they just lost to an upstart team that was really hot for a round, that's all. It happens sometimes. They'll be back next year. Eh, they just lost to a better team this year, that's all. It happens sometimes. They'll be back next year.