Look, if you're happy with what the CF-18 has done in the last 30 years—and I am—clearly it's suitable for the North American mission.
In terms of the overseas mission, the decision that would need to be made is whether we want to be the tip of the spear on the first day of attack against an enemy that has highly capable surface-to-air radar and missiles. We haven't fulfilled that role. We leave it to allies. More recently, in places like Libya, our allies have used cruise missiles or drones for that mission.
There are also other serious questions as to whether or not our new fighter jets might be rendered obsolete in 15 or 20 years by unmanned fighter jets. Investing a massive chunk of our defence budget in an as-yet-unproven, fifth-generation plane that might become obsolete fairly quickly has always struck me as a bit of a gamble.