They will.
Perhaps in 10+ years if AC follows its current fleet strategy. The 45 A220s on order/delivered are only targeted to the mainline and AC does not typically acquire brand new aircraft for Rouge (save for a handful of A321s a few years ago). It's more likely that Rouge will continue to take on the aging A319/20/21s from the mainline fleet as more A220s are introduced over there, and Rouge shifts to narrow-body only service.