Monster Hunter + Splatoon + Pokemon or Yokai announced (no release necessary) and the Switch will do 2 million in Japan by year's end. 4 million would take a bit of a miracle. I honestly don't think Nintendo will get more than 10 million shipped worldwide, regardless of sales. They haven't had the fastest turn-around on shortages.
Retro Tech Select - My Youtube channel. Covers throwback consumer electronics with a focus on "vid'ya games."
Latest Video: Top 12: Best Games on the N64 - Special Features, Episode 7