Apparently Rizin 13 did poor numbers, and even the main event disappointed. Given what Sakakibara said recently that if ratings didn't improve Rizin wouldn't survive, we could be looking at the end game for the promotion sooner rather than later. Which would be a real shame, because they consistently put on really strong events.
If Rizin does die off, then expect ONE to make a major push to sign their bigger names. ONE is aiming to become the premier combat sports brand in Asia, showcasing MMA, boxing and kickboxing. They are also pushing into Japan. They would love to sign a lot of the fighters who competed on Rizin 13.
There is a lot of smoke and mirrors with ONE - most of their tickets are giveaways, half of their scheduled shows never take place, and the claims they make about audience figures/viewership are simply embarrassing - but if their finances can hold up for a few more years, *maybe* they could become popular enough in Japan, China and elsewhere to be sustainable.
The most likely outcome, of course, is that Rizin will kick the bucket and ONE will follow it 2-3 years later...