I think people really overestimate Dragon Quest these days. It will probably sell about 2m LT across all platforms in Japan, so I think Splatoon definitely has a shot at surpassing it. But it will be close anyway.
Bet with Teeqoz for 2 weeks of avatar and sig control that Super Mario Odyssey would ship more than 7m on its first 2 months. The game shipped 9.07m, so I won