At a press conference in Japan earlier today, Bushiroad Corporation-the current owner of New Japan Pro Wrestling and Stardom-announced that as part of its 15th Anniversary celebration, a joint NJPW-Stardom event will be held on November 20 at the new Ariake Arena in Tokyo. Hiroshi Tanahashi represented NJPW while Mayu Iwatani & Starlight Kid represented Stardom. More details are forthcoming but Tanahashi hinted at possibly a mixed/intergender tag team match at the event.
Ariake Arena was built for the 2020 Summer Olympics in Japan and would have a maximum capacity of 15,000 for wrestling, slightly more than Ryogoku Kokugikan (around 14,000 for pro wrestling but closer to 15,000 for sumo) and would likely put it behind only the Tokyo Dome in terms of capacity for pro wrestling.
More as it becomes available.