It really depends on if Nintendo continues releasing DLC for it, and if the DLC spawns hype.
If they release even one more major DLC that adds up to as much as this fall's pack is supposed to have, and they release it sometime strategic next year, then it'll absolutely give it the lifetime push it'll need to hit 10m.
Without that, I'm anticipating 7-8m, due to being a launch title and waning interest as time goes by, despite the quality of the title.
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