I have a feeling Murray will get lucky in the future and face a newcomer or surprise slam finalist. He might not win the final, but he'll at least win a set
Remember, Ivan Lendl was a 4-time finalist before winning his first slam
I'm NOT comparing Murray or his talent to Lendl, but just saying Murray has plenty of time to do better on the biggest stages of tennis.
That's exactly what will happen. Federer can't keep going forever, and Nadal is injury prone, so it's not too unbelievable to see a mug make the final with Murray, allowing Murray to straight set him and take the title. Plenty of mugs have made finals in tennis once and lost, it'll happen again.