Hello Everybody,
The results of the vote are in and the option to keep obsolete repositories in the current org won by a large majority (9-4). The initial feedback that I got on the mailing list looked like it is going to be a tie, but the doodle made it easy to get feedback from people that did not get involved in the initial email thread, hence almost double the vote participation.
As a result, the option to create a separate archive org will be tabled indefinitely. The deprecated repositories and projects will be kept in the current org but marked prominently as such and write access will be revoked on all of them.
Thank you for voting!