And 2013 was just a bad year for him in general (by his standards.) Got silver at Worlds and ADCC instead of gold, and it was the first year of adjusting to owning and operating an academy, full time. He has 2 three-peats at Worlds, with 2013 being that off-year. Given that his off year is still better than what 99.9% of the population could ever dream of, I agree that his dominance is hard to match.
Also, not only has he had sustained dominance, but he gets better and better, and continues to innovate his own game and spread the knowledge. You see him doing things like winning the Worlds with all cross collar chokes from the back in 2014. Or going to Japan in 2015 and winning with all armbars on the same arm, and you start to think he's not satisfied with just winning but rather how he wins.
I don't know how much more he has in the tank. I assume he will do worlds this year. I hope he does one more adcc too. I love his no-gi style and miss seeing it in action. If he retires today he's a legend forever.