According to the newest trailer, Rainbow Six: Siege will implement Nvidia HBAO+ for better shadow effects and improved ambient occlusion, TXAA anti-aliasing as well as support for Nvidia G-Sync technology, which should provide smoother, stutter-free gameplay on G-Sync enabled monitors.
At its Geforce.com site Nvidia has anounced that the recommended GPU for running the game at 1920x1080 and high level of details is the GTX 960, while in case you want the same level of details at 2560x1440, you will need the Geforce GTX 970.
Nvidia was also keen to mention that Tom Clancy's Rainbow Six: Siege is also a part of the Bullets or Blades bundle which allows you to chose either that or Assassin's Creed Syndicate with Geforce GTX 970, GTX 980, GTX 980 Ti desktop graphics cards or GTX 970M or above GPU-equipped notebook.