Well remember when Fed was sweeping the slams everyone was saying they can't see Nolé or Murray getting a chance.
In 2011/2012 they were saying only nolé will win writing off Nadal and fed and what happened Nadal and fed sweeped up the French and Wimbledon.
Nadal came back winning 2 majors in 2013 when I remember Sue Barker and Tim henman said after 2013 Wimbledon final only nolé and Murray will fight for major titles.
Murray hasn't won a slam since and it took 1 year for nolé to pick up his next slam.
So predictions are hard to make. Who saw a cilic and nishikori final last year US?
In an interview Roger said anyone who plays sensational tennis for 7 matches can win a slam. He looks for longevity and obviously only the big 3 have been able to sustain semis and finals for like 12 years straight.
It's only now where it's perhaps beginning to change, even though 3 of the big 4 were in the semis last week.