A quick look at chessgames.com shows that except for draws Carlsen is defeating Nakamura virtually 100% of the time.
As any Wall Street analyst will tell you, past performance is no guarantee of future performance...
LOL @ btickler
Naka has made some impressive progress in the last couple of years. He might have even studied the WC's games 
when carlsen is here
Naka has won many blitz games against Carlsen, and vice versa. They've played hundreds, perhaps 1000s of blitz and bullet games against each other. And still, Carlsen has a large edge.
Personally, I'd find a WC match between the two to be hugely entertaining.
A Carlsen-Nakamura game is one of the rare cases when you can say "only two results are possible" from move one.