The current working population only partially funds the retired income. Significant part of retirement income in Canada is prepaid in the form of the CPP which is sustainable, institutional pension plans, and private savings beyond, often in the form of real estate and other assets. The money the current working population pays for retirees is towards OAS and GIS.

But in my opinion there's a better way to look at it by looking at the real economy, not the financial metadata. Can we feed, clothe, house and medicate our retired population? How many working people do we need to do that? I think given how much food we produce and waste and how few people produce it, that food isn't a problem. Neither is clothing. Housing on the other hand could be a problem since it already is. The same is true for healthcare. Can these be solved so that we don't reach a place where we run out of people to sustain the retired population? Housing can for sure. Once built it requires a lot less labor to maintain. Healthcare, isn't that obvious. Personally I think it's solvable but I can't present an obvious argument.

Finally, we have acute income problems with the working population today. As in, a good chunk of the working population can't afford to live where it works. If we don't solve them, any real problems with retirees become worse. For example PSWs being close to minimum wage workers, can't afford to live where they have to care for retirees.

I would say it's a self solving problem. There's a negative feedback effect between economic outcomes and population growth. Plus shitloads of automation technology reducing the demand for certain kinds of work. We don't need to keep suppressing wages by flooding the labour market.

Immigration with the express purpose of keeping labour costs low (which is the Liberals' stated reason for their current approach) is basically trading human dignity in the form of a living wage in exchange for subsidizing businesses who refuse to pay their workers more.