It appears that Kenny Omega leaving for All Elite Wrestling did force New Japan Pro-Wrestling to change plans.
According to Dave Meltzer of the Wrestling Observer Radio, the original planned main event for the G1 Supercard at Madison Square Garden was set to be a rematch between Kenny Omega and Kazuchika Okada. Of course, Omega dropped the IWGP Heavyweight championship to Hiroshi Tanahashi at Wrestle Kingdom 13, who in turn, dropped the belt to Jay White at New Beginning.
Reportedly, the current plan is to have Jay White defend his title against the winner of the New Japan Cup, who might be Tetsuya Naito, Kota Ibushi or Okada himself.