As previously announced, the Canonical Kernel Team (CKT) has committed to target the Linux 6.17 kernel in the upcoming Ubuntu 25.10 (Questing Quokka) release as part of a more aggressive policy towards release kernel selection. With the recent release of Linux 6.16 we now have a much clearer idea of when 6.17 is likely to be released, as of this writing being tentatively Sept 28, 2025. The current 25.10 release schedule has Kernel Freeze set at Sept 25, which means that there is a strong possibility that Linux 6.17 will still be in a final -rc state at the time the kernel needs to be frozen for the 25.10 Final Release. Therefore, the CKT are announcing that Ubuntu 25.10 will potentially be an Unstable Release from the perspective of the kernel and will be henceforth working with that assumption until such time as conditions warrant a change.
The details on what an Unstable Release is as well as its ramifications and what you can expect can be found in the original policy post Kernel Version Selection For Ubuntu Releases, which has been recently updated to reflect refinements made over the last year.