Maybe not a surprise to some, but now it's more or less confirmed by the president of Nintendo, Furukawa. Serkan Toto has some highlights from a recent interview. It also includes that the Switch is selling software faster than any other Nintendo hardware ever. 1) Japanese daily Nikkan Kogyo Shimbun released a (very short) interview with Nintendo president Furukawa today.
He says Smash Bros sales passed 5 million globally in week 1.
Says Switch is the home console seeing the fastest software sales so far in Nintendo's history.
An incredible start and I might guess that we have Smash over 10 million soon. Not much else to go on, but if Furukawa says week 1 it might already be.