I'm actually expecting Zelda TOTK first fiscal quarter sells to be about 10M copies sold. People can't underestimate how much hype this game will get once we get close to release.
Your post could age like milk, so you better hope that today's Direct doesn't show us a Tears of the Kingdom that is an evolution of Skyward Sword rather than a better Breath of the Wild.
During the past 25 years the Zelda series went up and down. Ocarina of Time (well-received) was followed up* by The Wind Waker (not well-received) which led to Twilight Princess (well-received), followed by Skyward Sword (not well-received) which led to Breath of the Wild (so well-received like it hadn't been the case since the original The Legend of Zelda). Nintendo has to buck this trend for once.
*I am not counting Majora's Mask as the next big Zelda game because its working title was Zelda Gaiden (read: sidestory), hence why it lacked any reference to Ganon.
Legend11 correctly predicted that GTA IV will outsell Super Smash Bros. Brawl. I was wrong.