The North American PR Twitter account for Kingdom Hearts Union χ[Cross] has tweeted that the first update of the two-part finale will be going live for the global version tonight at midnight PT. (3:00 AM EDT)
This is exceedingly odd, seeing that the Japanese PR Twitter account for Kingdom Hearts Union χ[Cross] has stated that their update will be available on April 30th. There is always a chance that either or both accounts could have accidentally posted erroneous information. Still, we will be finding out if this statement from the global account is true later tonight.
UPDATE: (04/29/2021) The announcement tweet from the English PR account seems to have been posted a day early. The story update should be tomorrow (April 30th) at 15:00 JT for Japan and at midnight PT for Global!.
UPDATE (04/30/2021): Quest 978 "What Comes After" has been updated on both JP and Global! The quest only contains story cutscenes and doesn't have a mission attracted to it. The quest is also available on Proud Mode.