A lot needs to go right to make a deep run. Coming back from the dead against Pittsburgh and going toe to toe with Carolina and coming up on top helped them get here. Both were far from guarantees to happen, and the Ranger beat significant odds to overcome those two obstacles.
There are no guarantees in this sport. Ever. The window is officially open now, yes, one year early at that, I would say. The way this team's roster is constructed, they're a season ending injury to Shesterkin or Zibanejad away from another lottery pick. Drury still has his work cut out for him in constructing this roster. Even when you make the playoffs, a lot can happen. There's no good matchup for the Rangers. Pittsburgh, Washington, and Carolina are their most likely Round 1 and 2 opponents and would still give the Rangers fits. They're not head and shoulders above them to win it in a sweep or in 5 like Colorado was to their competition. All it takes is a few bounces either way and fortunes change.
Provided this team lucks out on injuries, they SHOULD win the division next year, if not, another 2nd place finish behind Carolina. The X-factors are going to be who's the second line center next year and how much of a step forward Lafreniere and Kakko take.
I like your optimism that the best is yet to come, but is it? It is so hard to get back to a conference final, never mind a Cup Final or winning a Cup.