It's unlikely that JMS would be the one making the announcement.
That is one of the "perks" the studios and networks reserve to themselves and they get Annoyed if someone "steals their thunder".
All through the Original run of B5, JMS had to wait for Warners or PTEN to announce, even though JMS sometimes Knew as much as a month before the official announcement.
The Business & Publicity people have their own schedules they like to follow when making announcements about new shows and series renewals.
Sometimes it's nothing more than an "everybody announces in Mxx" sort of thing.
Sometimes they think the "Mystery" will pull in extra viewers when they finally DO announce.
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Do not ascribe your own motivations to others:
At best, it will break your heart.
At worst, it will get you dead."