I'd been coming around to your rather bleak view -- Matthews's departure inevitable as the Shanaplan window closes -- but, since the new regime's taken over, I'm feeling this could go differently.
Part of that is draft luck, but the result is what it is: is there any team that's had as good a regular season win percentage as the Leafs over last 3 years (even including last year's disaster) that boasts a talent like McKenna? That's added as many guys who might be something in 2-3 years? The Athletic ranks teams' under-23 pipelines. I think the Leafs are in the top third in the league there, and in points over the last few seasons.
Other players around the league seem to be responding positively. The Leafs got the top UFA this summer to sign here. He's a hometown guy, so maybe that doesn't mean much, but then Marchenko extended here, after (according to Friedman) being very skeptical of the team when trade rumors floated several months back.
If I were Matthews, I'd still probably sign my next deal as a short term thing with some guys I like to play with (Werenski? McDavid?) on the team that can fit us and is closest to the Cup. But he might like Toronto more than I do! It's a pretty great city if you're rich