We haven't heard anything about the co-op Siege spin-off Rainbow Six Quarantine since its announcement at E3 2019, but thanks to the power of investor calls, we have a better idea of its release date. According to Ubisoft CEO Yves Guillemot, Rainbow Six Quarantine will release before the end of the fiscal year. That translates to any time before April 2020.
Quarantine was initially announced as an early 2020 game, but this narrows in the date further. As Game Informer points out, Ubisoft has a pattern with its releases in the beginning of the year. The company usually releases a game in either January for February, and Quarantine is the most likely candidate for that slot.
The plot is slightly thickened by two other early 2020 Ubi games: Watch Dogs Legion (March 6) and Gods & Monsters (February 25). Quarantine isn't a direct competitor with either game, but Ubisoft will likely put some time between each release. A good bet is late January or early February.
Thanks, Game Informer