As evidenced by the E3 demo, Rainbow Six Siege will have an emphasis on its multiplayer component.
Speaking to IGN, Ubisoft Montreal creative VP Lionel Raynaud explained why Rainbow Six Patriots was cancelled, “We were tired of single-player, scripted military missions where things appear triggered by player presence. We want to refresh that. We want the same level of intensity and surprise scripted scenes used to have, but within a multiplayer game.“
Thus, Rainbow Six Siege was born. The game has a development team 150 strong, and is being developed by Ubisoft Montreal alone. The title has been in development for 18 months.
While Rainbow Six Siege will have a single-player option, the campaign missions will be like a Mega Man game; you can play them in any order you like. Other than that, we know very little on campaign details.