Historically, the next season starts ~16 days after the PTR ends: ~11 days till the season’s end and a 5 day gap between the seasons.
That would put S29 end on 24th and S30 start on the 29th. But that’s in the middle of a holiday week.
Moving it forward a week puts season end on the 31st and season start on the 5th. But the season end still falls in the holiday week.
So maybe another week? The 7th and the 12th, but that seems a long way off.
They could blitzkrieg it and have the season end the 17th and season start the 22nd. But that’s not likely because they almost always gives a ~2 week notice for the season end. EDIT: As suspected, this didn’t happen.
So who knows.
The 31st and 5th are a possibility in my mind. I suspect not much is needed to end a season, so it falling on New Year’s Eve may not be an issue. The real manpower is needed for season launch when all the problems hit, which would be the 5th (a regular day).