I spent a month trying different layouts on the Twiddler 2, but ended up ditching it. I could only get up to ≈25% of my normal typing speed. And no matter what layout I experimented with, some keyboard shortcuts were a huge pain. There just weren't enough meta keys.
I do think there's something that could be made in this space, but it would be a niche product. Standard keyboards require no up-front training. A complete novice can use one just fine (although slowly). Chording keyboards require a significant time investment before you can type a single sentence. That up-front cost might be worthwhile, but it really hurts adoption.
In addition to that fundamental issue, most chording keyboards today have two big implementation problems:
1. They are USB instead of Bluetooth. That makes them much less convenient for mobile usage, where they have the greatest advantage over standard keyboards. Instead of grabbing the chorder and typing, you first have to plug it into your laptop, tablet, or phone (if that's even possible).
2. They lack a decent pointing mechanism. The Twiddler series uses a thumbstick. I would vastly prefer a trackball under my thumb. If done right, it would give the ideal combination of speed and precision.
Now that VR is poised to become popular, I think there's a larger chance that someone will make a high-quality chording keyboard. Still, I wouldn't put money on it. Learning to use one proficiently is almost as time-intensive as learning to play an instrument.