Anybody expecting something for the die-hard Nintendo fans or traditional gamers will be disappointed. This is likely the peripheral-driven, audience-expansion software Kimishima has been talking about in interviews with Japanese newspapers - it'll be more a Wii Fit style new IP (or 1-2 Switch) than character-driven IP like Arms or Splatoon. What will be interesting to see if this genuinely moves Nintendo's non-traditional mass-market software philosophies on in any meaningful way. The fact it's peripheral-driven and for "kids or kids at heart" might mean this is another push at toys-to-life, but that wouldn't quite square with "new interactive experience"; unless Nintendo have found a way to meaningfully develop that area.
The better news for us more traditional gamers is that there have been rumblings throughout the week that this was coming. The same sources suggested that Nintendo will follow this up next month with a full-length Direct aimed at their more traditional audience and were on the ball about Nintendo's broadcast last week. I'd expect there'll be some backlash online too, when this ends up being closer to a ROB revival than an F Zero revival, so Nintendo will want another Direct before long to reassure their core audience - the way they announced NX at the same time as their mobile games push, for example. At any rate, it certainly appears to be the case in the last couple of years Nintendo have been less water-tight than they were a few years ago.