At an average of $11.64M per season, Matthews will almost certainly eclipse an AAV of $14M and possibly even $15M, depending on how much the cap increases. Given reports that the cap will increase between $5M and $7M at the end of the 2023/24 season there is no reason for the Leafs not to hand Matthews a blank cheque and an 8-year term on the deal.
Unfortunately, Evolving Hockey's contract projection model is suited for the offseason and salary cap we are currently in, but if Matthews was able to sign an extension this off-season, they projected an 8-year contract that would pay him just shy of $13.9M per season.
If we take that projection into consideration and the rising cap for when his extension would kick in ($88.5M - $1M increase next off-season and $5M the next), the AAV for Matthews' next contract will likely be between $14.8 and $15.3M. That may eat up most of the increased cap, but the Leafs will also have almost $11M coming off of the books in TJ Brodie and Jake Muzzin, so there will still be room to possibly re-sign Nylander and bring back other roster players.
Of course, those numbers could increase should he win another Rocket Richard, MVP and the Leafs make it past the first round. Matthews is already better defensively than both Connor McDavid and Leon Draisaitl and is able to score at a much higher rate at 5-on-5 than both, meaning he doesn't need to rely on special teams to produce.
Matthews will be 26 when his current deal expires and will still have room to develop into an even better two-way superstar. Until next summer though, it will be a season full of dissecting and discussing what his extension will look like and we will all be sick of it.
It's funny that David Pastrnak and Nathan MacKinnon are eligible for free agency in just 10 months, not 22 months like Matthews, neither of these players are being isolated the way Matthews is in terms of potentially hitting the UFA market..