According to the latest report, the Switch version stand at 8.48 million. Combined with the WiiU version, it is over 10 million.
A quick top 5 of other games (Stand alone):
The Legend of Zelda: Ocarina of Time (N64) - 7.60 million
The Legend of Zelda: Twilight Princess (Wii) - 7.18 million
The Legend of Zelda (NES) - 6.51 million
The Legend of Zelda: Phantom Hourglass (DS) - 5.09 million
The Legend of Zelda: A Link to the Past (SNES) - 4.61 million
Pretty well done. Do you guys think BotW will go over the combined total of OoT?