Can't verify it personally but apparently on SEGA's Yakuza stream earlier today it was said the announcement is coming in the evening PDT, so should be towards the start of the event in that case.
Likely part of the opening section, so be sure to get watching early. Also, there's a difference between the Twitch and YouTube streams apparently, with one showing just the stage, and another being stage + a broadcast. No idea which of these will have the announcement, so keep your eyes peeled.