Update: Gamestop has updated the Rainbow Six Siege page in its listings, removing the October release date. Another hint that October 16 is really going to be Siege's day one? We'll see...
Original news: Looks like Ubisoft is all-in with Rainbow Six Siege for this Holiday season.
Based on the listings from Gamestop Italy, that has just introduced the closed beta and what seems to be the official cover of the game, the shooter will be available on October 16. That's Friday, the day that always witnesses important releases in Europe.
Looking at the description supplied by Gamestop, furthermore, it seems that Rainbow Six Siege will be strongly based on the procedural destruction of the locations.
We'll be following the situation as it evolves, waiting for official statements from Ubisoft. Stay tuned!