There's a concern that if it doesn't go forward, as people get the tax hit, they'll find it a less than desirable vehicle, and the problem is that people will either try to manage their own portfolios without having the expertise, which will likely result in less savings for retirement, or they might not invest at all. They might invest in GICs, and you can't really retire off the rate of return you get today on a GIC. It might dissuade people from using target date funds, even though around the world that's becoming the default investment option of choice for people saving for retirement.
On November 9th, 2017. See this statement in context.