Kaido and Black Maria confirms that the announcement involves Yamato
So it surely is either announcing:
1- Yamato's marriage from Big Mom daughter (mosat likely) considering BM alliance happens through marriage.
2- Or that Yamato starting from that day, he will have a specific rank on beast pirates, like getting promoted and becomes "vice captain" as an example... but this is less likely...
Yamato political marriage is very likely! But who would it be? Could it possibly be Pudding? Is Oda gonna bring her back to that same plot for more annoying "Sanji-pudding" stuff? Please no!
But it's possible
Or is it sexy Galette?
If it is pudding, does that mean the other half of Big Mom pirates (Katakuri/Oven/Cracker) are coming and on their way???