I'm going to doubt this rumor. It's only been 3 years since Color Splash and it was a big flop. Why would Nintendo be in a rush to get a new game out the door?
They've become more aware of what fans want and making games they want made this generation, imo. People have been begging for this for over a decade. If they think it will sell really well, they could have reprioritized schedules to push it up further.