As far as I remember Martin did underline and stress out that it is release date. Not announcement. That trailer we saw at fan gathering was 'DLC' trailer, which as I mentioned earlier will be free Story DLC for everyone! Next week, announcement may be still be in form of the news on monday in form of - 'It is available now!'
Because monday is all in all next week
IIRC - This free story DLC is called Horizon or sth Horizon/Horizon sth - hopefully not Event Horizon
Trailer is rather short, but I would say pretty cool