This year is not Novak at 28! I've said he can dominate this year and next but that's about it. Will he win 3 this year? Potentially but 2 more likely... 3 next year? Very unlikely. Murray, Del Potro etc. are going to be fighting it out too.
Plus pretty sure Rafa will kill himself for the French & Wimby - same goes for Fed at the Olympics - it's a long long road to 6+ more grand slams.
Here's hoping all the top guys stay injury free too - you just never know what will happen.
Say Novak dominates 2 more years like you said .....Del Potro and Murray will be non factors in 3 years .....