I'm more curious who would be in the 25-26 Heritage Classic (or whenever - they tend to run roughly every 2 years, but that's not etched in stone).
Looking - curiously no eastern team has ever "hosted" a Heritage Classic (2022 in Hamilton lists the Sabres as the home team versus the Leafs). 2017 saw the Leafs host the "Centennial Classic" however versus Detroit. As I'm researching apparently Ottawa also hosted an outdoor game against Montreal in 2017, although I can't find it had any special name.
So if you want to go by who is "due" it would be Montreal - but Molson Stadium seats 23,420 - scarcely bigger than the Bell Centre's 21,105. Olympic Stadium ahs the size, but with a permanent roof doesn't seem like it would really fit the bill.
The next team that is most "due" would be Calgary (2011 Heritage Classic), but they literally just played in the 2023 game in Edmonton, and lots of fans did travel.
Beyond that - who knows? Montreal at Toronto would draw huge for sure. Is there a oood neutral cite I'm not thinking of (Regina hosted back in 2019)?