You had the end of Season warning, they don't give a specific date for the final Season of the expansion, just like they didn't last expansion.
https://worldofwarcraft.com/en-us/ne...he-post-season This was your end of expansion 'Season Announcement' last expansion, 7 days before the pre-patch official date was announced, and 12 days total before the pre-patch hit.
https://worldofwarcraft.com/en-us/ne...xpansion-patch This is your end of expansion 'Season Announcement' for this expansion, 5 days ago, what is I'm assuming now likely to be 15 days before the pre-patch hits. Which means we'll likely see an official announcement for pre-patch being October 6th next week, unless something is announced in the next hour or two.
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Why tomorrow? Friday work day ends in like an hour for them? They're not going to announce on a weekend. I mean nothing is stopping them from doing it but Blizzard are well known and documented for doing nothing on weekends in terms of announcements/development/hotfixes.