But you aren't arming for short term threats. Any fighter you choose now will still be serving in 2050.Relations with Russia have now a lot better chance of improving after Trump assumes his presidency. Australia is in a tougher neighborhood than Canada- like late R. Reigan said: "nations don't trust each other because they're armed; they arm themselves because they don't trust each other!" That said, at least I was right about suggesting the F-16- it has 1 engine, not 2, and still in production! New variants of J-39 could also be considered. In fact, Swedish & Canadian climates r similar, with long coastlines to defend! Lastly, if anyone complains about Canada's falling behind her NORAD/NATO obligations, they should thank USA for helping to terminate the Arrow program that killed all future domestic-built interceptors!
Any 4th generation aircraft you buy now will be horribly outdated and outclassed by then.
With the F-35 you will get ongoing support and upgrades that will keep it viable for at least a few more decades.