I say the same thing, too. It is a lack of imagination that leads us to think that what happened last year will happen this year. Djokovic is the poster child for that not being the case. However, as you say, it doesn't mean that Rafa is not the formidable best on clay. Same as Roger on grass. And let's not forget how few surprises we've gotten over the last decade +. I think we're entering the shake-up years, but as long as Rafa and Roger are playing well, frankly, reality hasn't proved us too wrong.
Yes it did: Talking about current decade:
In 2017 no one saw neither Federer nor Nadal coming. They both did.
In 2016 no one saw Murray turning the tables over Djokovic, stepping up to #1 by winning a major and YEC
In 2015 no one saw Wawrinka winning the French
In 2014 no one saw Wawrinka and Cilic winning majors
In 2013 no one saw Nadal storming back as he did (not even his rational fans, sorry to put it that bluntly)
In 2012 maybe nothing strange happened, I do not remember
In 2011 no one saw Djokovic coming.