This comes from a NintendoLife interview with Two Tribes' Collin van Ginkel...
First of all, can you talk us through the reasons and thoughts behind RIVE being delayed for Wii U, or perhaps being moved to NX instead?
It's very important to us that Nintendo users will get a great version of RIVE, but unfortunately we don't know at this point when or how we'll be able to deliver this. There are two main reasons for this, one technical and one business related.
The Nindies demo in 2015 was specifically optimized to perform well in hand-picked levels and didn't manage 60FPS consistently. We've added a lot of stuff since then and we haven't been able to reach the performance level required yet. We won't release RIVE unless it's a solid 60FPS, and if that means delaying it to a future platform, we will make that call and make sure Nintendo fans get the perfect experience.
The market has also changed. The game was supposed to ship over a year and a half ago, and things are a lot different now. Nintendo is exiting the Wii U market early in favor of the NX which means a long tail in sales is not looking likely. So that is the business part; do you release a game on a platform in its last days or on a new one that's better suited and can reach gamers for years to come?
How long do you think it'll be before RIVE arrives on Nintendo hardware?
At the moment I can't easily answer that. We're going to try one last time to perfect the Wii U version, but if that fails we'll need to focus on the future.