Matthews has 3 full years left - 3 years ago, the Predators, Jets, Wild, Ducks, Sharks and Kings had 117, 114, 101, 101, 100 and 98 points, respectively.
In three years, the NHL will look completely different but in a probably unpredictable way. Ottawa, Buffalo, Montreal and Detroit were all bottom feeders and still are, and those aforementioned teams were all great and are now all lottery teams (with the exception of Winnipeg who have still done little to nothing in the postseason)
if Matthews goes to free agency, he is going to pick somewhere that fits his priorities. Arizona is a place that makes a lot of sense for lifestyle, being close to home and for getting a big payday, but with them being relocated as an always looming threat, or maybe his aspirations to be a Stanley Cup champion one day, even Arizona isn't a surefire. What if Matthews goes there and they get shipped off to Quebec? What if they get Wright and Bedard somehow and don't want to spend 12+ million on Matthews?
LA makes sense if he wants to be in LA - but Doughty and Kopitar would be the first people to tell you that nobody cares about hockey in California. A huge reason Danault as an example wanted to sign there is because nobody really bothers hockey players - it's also the reason Toffoli wanted to sign in Montreal, because he said he wanted to be in a hockey market instead of walking down the street and nobody recognizes you. If Matthews wants to be a celebrity, Toronto is one of the best fits for him - NYR, Montreal, Toronto, Chicago are probably the four best markets to play in if you want to be in the spotlight.
I think the 5 year deal was smart as it gives him flexibility if things aren't going well. Generally speaking, I think trading Matthews is a fantastic idea but only to alleviate the top-heaviness of the team. I would keep Marner because you know he will remain loyal to the team as a hometown kid and he is an elite playmaker, you keep Nylander because he's the best bang for your buck and flourishing into an elite player, and you keep Moe and make him your next captain. Tavares can be a great transitional 1C if you can't move his contract, but in an ideal world the Leafs would dump both to open up 22m in cap.
Imagine something like Matthews for Lafreniere, Miller, Chytil and a 1st - you fill a few holes and can probably maintain all three of those contracts for the price of one. Eat 2m of JT's $ and move him to Chicago for Strome and A.Nylander + a pick - suddenly the room changes, you have a ton of new faces and talent, and your cap is WAY more manageable.
