You may or may not have been aware the Ubisoft's Rainbow Six Siege beta has already went live last Thursday. Well, it turns out, Ubisoft needs more time to collect data to ensure that the game will have a stable launch in December. Thus, the beta will now extend until October 4th.
Ubisoft posted the latest update detailing this on their blog. Furthermore, anyone who has already participated thus far, and played at least one match, will be receiving an email from Ubisoft containing extra codes you can give to your friends. Those codes, however, will match the system that you're currently playing on, meaning they can't pick and choose which system to play on. Additionally, starting Friday at 8PM EST, there will be Double Renown awarded to players which will help with unlocking additional operators, attachments and skins.
You can still sign up for the beta on this page, however, the page will be taken down tomorrow.
Tom Clancy's Rainbow Six Siege will release on December 1st, 2015 for the Xbox One, PlayStation 4, and PC.