Carlsen is good but he is not a computer. He will make some mistakes and lose some games where he was expected to win.
What if Nakamura never beats Carlsen

Caruana = Karpov
NOT Aronian, if anyone still thinks he's a rival to Carlsen then you are delusional.

If Caruana is Karpov then who will be Kramnik?
In Kasparov's career, only two players gave him some trouble...they were Karpov and Kramnik.
Kramnik came near the end of Kasparov's career, so Carlsen's Kramnik might be Wei Yi or another rising youth.
Nakamura will never beat Carlsen. Ever.
I can see Carlsen's score on Nakamura as +45-0=87 in 30 years.