Yeah, he's actually serious about this, the news is already out on Yahoo headlines. He gave an interview explaining that starting in 2019, RIZIN would consist of 3 pillars/arrows:
4 large scale shows at Saitama, considering the slowly but steadily increasing attendance figures at the venue he aims for an eventual goal of 25000 on NYE 2019
4 mid scale shows on the level of RIZIN 12, designed for venues with a capacity of ~5000. Called RIZIN 12 a successful test run of that concept.
12 small scale shows with cards designed for venues on the level of Korakuen Hall, which would mean for a capacity of ~2000