There are generally two factors in selecting National Team in these cases:
1. Identity
Players select a nation with whom they identify themselves more. I don't see any advantage, theoretically, for Canada here, considering he lives in Finland for most of his life and plays in their league. Yeah, it's possible that somehow he's more related to Canada, but it seems unlikely.
2. Rationality
Players select a nation that gives them bigger chance to succeed. Nowadays, with Finland producing year-by-year elite talents, giving underagers chance to compete on U-20 Junior Champs and getting so much hype for development of its players - is there any advantage of Canada here? Yeah I'm not suggesting that Canada isn't good anymore in producing elite talents, but ask yourself if Lundell would have had any opportunity to play this year on Junior WCH for Canada, considering how limited chance was given to Lafreniere? And I don't think that moving to WHL is a good idea considering he will be probably regular SM-liiga player as -2 draft eligible player, basically I can't imagine a better development path.
He's basically on Barkov level currently with his production, but because of cutoffs and being 3,5 months younger, he's -3 draft eligible right now, while Barkov was -2 in his 15yo season, that's insane. Kakko being almost a year older didn't regularly play in Junior-A level.
I'm not saying he won't select Canada, but it seems highly unlikely as for right now.