I don't think long-term really applies at this point (or ever really applies for a top-6 group).
I think what that top 6 shows is that, if everything breaks right and players continue to develop, Montreal has a potentially strong top-6 internally (without needing to trade, draft or sign someone). I don't think it means that it can't/wouldn't be improved on or changed, but more that Montreal's shifting to another stage of the rebuild. That doesn't mean the rebuild is over.
For frame of reference, I'm thinking of the Devil's after 2020-2021. They had a lot of talent at forward (Hischier, J. Hughes, Bratt, Sharangovich, Zacha) plus good forward prospects, and some decent D. But they still weren't ready to compete and continued to add in other areas.
Its the difference between just trying to cobble together lines that work and figuring out what you need to take the next step.