Only just ticking onto 24hours since a 'reliable' outlet published that it was likely to actually be happening.
If the official approach/trigger only happened yesterday (which given the timing of news breaking seems pretty likely), then with the amount of legals involved (potentially for multiple people), I'd be shocked if they'd managed to get it wrapped up and ready to be announced this side of lunchtime.
As is the case with player transfer announcements as well- the clubs involved will agree on a time between them once they know it is 100% completed. It doesn't get signed and announced immediately anymore.
No doubt Bristol City's media team will have spent the morning creating their graphics/video for the announcement. They may want to line up a convenient time for their local media also.
Ours will be in preparation for tonight's game and doing BAU stuff.