It looks like Ubisoft has no plans for a sequel to Rainbow Six Siege . At least not now. This became known from the session of questions and answers with the creative director of the game Leroy Afanassoff.
Siege is an evolving game. Siege of the future will be radically different from today’s game to the point that we could call it the second part. However, as a team, we strongly believe that we will be able to bring about these changes gradually, as part of the development of the current game.
The second part implies radical changes, for which the shooter community is definitely not ready, so Ubisoft will continue to develop the game, and not make a sequel. As fans may not notice, the team is constantly improving the title to prepare it for larger changes.
Rainbow Six Siege is available on PC, PS4, PS5, Xbox One and Xbox Series X / S.