He probably has at least 3 good years in him. Cap is going up quite a bit, so I don't see it being that much of an impediment.
Bigger issue is they have an aging top 4D that's locked in for the next 4 years.
Tanev is 37 this year & has 4 more years.
McCabe is 33 this year & has 4 more years.
Rielly is 32 & has 4 more years, although it sounds like they hope to trade him.
Then there's OEL who turns 35 in July, and has 2 more years.
Raddysh is a youngin' in comparison. Carlo is also 30 in July. 6 guys on D, all 30+. It's totally a win now team.
If any of these players have a sudden drop off due to age, Leafs are screwed anyway. We'll see how healthy they can stay too.
Imo, Leafs are in rebuild mode if Matthews doesn't re-sign next summer. But, they won't officially do it until 2029. They'll try to give Philadelphia & Boston non-lottery picks.