We will never have "Credits"
I mean, sure, we will probably in the near future even use our cellphones to pay for things, and soon after that maybe we'll have "credit chits" or some other sci-fi such nonsense like that... but something will never cost "5,000 credits."
I say that because if there is one thing I've learned in my short time on this earth, it's that we can never agree on anything. We can't even decide what file format to use for movies, let alone what single universal currency we should all use. Maybe we'll have New Pan-American Bitcoins or DigiEuros but to think that we could all agree as one planet to use "Credits"? That's just nonsense.
And I don't even want to think about how impossible that would be if we ever travel the depths of space and meet other races.
But it would be nice though!