I think it’s a little too early to rule that out completely, as we still don’t know what NDcube’s next project is. They have made seven Mario Party games in the past 10 years, and they have a new game almost every year. Their next project could be a massive DLC for Mario Party: Superstars, or a new Mario Party game entirely, or a new game unrelated to Mario Party (they’ve also worked on Clubhouse Games: 51 Worldwide Classics, a few Animal Crossing spin-offs, the Wii Party games, and Wii Play: Motion).

Until we’ve seen their next game though I think it still remains a possibility, although it would likely be one large paid DLC given how long it’s been, rather than small incremental updates.