I have no idea how credible this firm is but i trust their sources: "SuperData noted that it collaborated with market researcher Gfk and the Japanese gaming publication Famitsu to come up with the figure."
And from what i have read from the launch in other countries, i have no doubt the numbers are that good and that demand is there.
Just a little side note: here in Portugal (aka Sonyland) it sold more in it's opening weekend than any other Nintendo console.
Believe me, it's that big of a feat!