as outlined in https://lists.debian.org/debian-python/2020/07/msg00023.html
it's now time to go ahead with the 3.9 defaults change. https://lists.debian.org/debian-python/2020/11/msg00012.html has a status update about outstanding issues, focusing on the key packages. While not every fix is available in unstable, there is upstream support for those key packages, and the status is covered in bug reports. this transition should be less dependent on other transitions as we already have 3.8 and 3.9 extensions migrated to testing. The only entanglement should be with packages only supporting to build with the default python3 version, and introducing a transition themself. It might be good to wait on finishing the perl transition, but currently there's no entanglement at this point. Matthias