Ubisoft revealed the name of the upcoming new Assassin's Creed formerly known as "Victory" today.
Assassin's Creed: Syndicate will be released October 23rd, 2015 for XBOX One and PS4. Windows will be released sometime in Fall as well. Since Fall starts on September 23rd it could even be earlier for Windows. But based on all other Assassin's Creed releases I would say either same day or later.
Links to released videos here!