Looks like it is well on its way to being the best Smash of all time. It seems exclusive games on Switch are breaking all kinds of sales records. A lot of this probably has to do with the fact that due to the hybrid nature of the console, many adults who loved gaming but have trouble finding the time can jump back into the hobby naturally with Switch. This means that these sales are being driven by more than just long term Nintendo fans, which leads to potential growth opportunities for the brand as a whole.
And we still do not even have half of the 3DS userbase. The conjoined nature of both handheld and home console is likely to focus sales as well, and push sales to new heights as well for lifetime sales. It is already outpacing what Smash 4 did for WiiU and 3DS combined, so as more people make the jump from 3DS to Switch sales should keep momentum going forward, making this another big evergreen title for Nintendo.