I think this is a great idea & I'm sure if employers were willing to integrate or adapt their pension schemes to include BTC then it's a definite possibility that people would be willing to use it.

Most pension schemes with banks or brokers make you invest a fixed amount of fiat that comes out of your wages every month over a number of years (say 30-40). A lot of them mess around with your pension pot by investing the money in stocks & shares to try & grow your final pot (with them taking a %) so it'd be no riskier for people using BTC instead.

I think this is definitely something that could happen in the future, I think it's probably a little too early now though for most people/companies to be willing to risk their pension using BTC.