Before Nakamura gave his notice, if you asked fans "what's left for Okada after he replaces Tanahashi as the ace?" there was a good chance that they'd say Nakamura. 'The Rainmaker' and 'The King of Strong Style' faced off on three occasions. Nakamura defeated Okada in the 2012 G1, a tournament that Okada would eventually win. Then Okada would defeat Nakamura in the finals of the 2014 G1 to win his 2nd G1 tournament and, finally, Nakamura defeated Okada in the 2015 G1 on his way to the G1 final (a match he'd ultimately lose to Tanahashi). While all their meetings took place within the confines of the G1, many fans were anticipating the day when Nakamura would challenge Okada (or vice versa) and the ramifications that would cause for CHAOS. Many envisioned a CHAOS civil war, with the overly-large faction splitting into two distinct camps under the rule of Okada and Nakamura, respectively.
However, the chances of that happening in the immediate future are looking rather bleak, so what now for Okada and where does CHAOS go from here? It's safe to say that the group is now Okada's to do with as he pleases. Without Nakamura, Okada's the only legitimate main event star in the faction and, while their numbers are a bit thin in that regard, there's no reason someone can't be elevated within the group. To my mind, that someone should be Tomohiro Ishii and if anyone's going to stick a knife in Okada's back, it should be him. I can picture Ishii sitting in power over CHAOS like a daimyo from the Japanese Sekgoku period, kicking Okada (and probably poor YOSHI-HASHI) to the curb as he usurps power. Artists depiction of Shogun Ishii;
This is all just fantasy booking, however, and it's probably more likely that Okada will be in the sights of Tetsuya Naito and LOS INGOBERNABLES de JAPON in 2016, but I do think there's potential for Ishii to become a major player in New Japan, rather than being chained to both the NEVER belt and CHAOS. Also, without Nakamura, what even is CHAOS? The group was formed by Toru Yano and Nakamura when Yano turned on his G.B.H. team-mate Makabe and, until Okada's return in 2012, CHAOS was entirely a vehicle for 'The King of Strong Style' and his increasingly eccentric persona that would see him become one of the most popular, charismatic figures in wrestling. Okada was just along for the ride and now, with Shinsuke gone, the faction needs shaking up in my opinion.