My best guess:
Arizona will offer sheet Matthews (13M AAV).
Isles will offer sheet Marner (12M AAV)
One of 28 teams able to do it would go for a 4.05M AAV on Kapanen.
Leafs currently have 23M of cap space next season, so right away, that's for sure one if not two of them gone unless they trade away someone else off of their roster. And then say they somehow manage to get 2 of them signed, they will be in a bind with their RD side depleted, Gardiner is gone, and most likely a few more ELC guys having to be thrown in the mix.
I say Montreal should (and will, since it's Bergevin) stay out of the bidding war and instead go the RFA route and offer Mark Stone 7 years, 60M.
If Montreal picks a top LD (Broberg or Byram) at the draft, and the additions of guys like Poehling, Suzuki, and others within the next 2 years, they will be set to be competitive if Kotkaniemi continues his progression.