From October, Games With Gold, the monthly titles redeemable by Xbox Live Gold (or Game Pass Ultimate, which includes it) members , will no longer include Xbox 360 backward compatible games. This was announced by Microsoft with an email that it is sending to subscribers, explaining that the service has "reached the limit" of addable Xbox 360 titles, and therefore from October they will no longer be present leaving only the Xbox One titles.

Nothing will change, however, for the Xbox 360 titles redeemed so far in the service: they will continue to be usable and downloadable even if you let the subscription expire (unlike those Xbox One that instead require the presence of the subscription after being redeemed).

Microsoft hasn't explained whether the monthly game release will be reduced to the two current Xbox One titles, or whether that number will be increased to make up for the lack of Xbox 360 titles. We will update you as soon as there are clarifications on this.