A counter to the non-repudiation of old emails is the fact that people who own their own mail servers can rotate their DKIM keys. So it's already possible for e.g politicians to have their email set up in such a way that they're insulated from leaks.
The argument here is more that customers of gmail and other email services are not offered repudiation as a feature.
"Rotating keys" isn't the important part. "Publishing keys" is the important part. "Rotating keys" is an implementation requirement of "DKIM with repudiability via eventually-published keys."
The argument here is more that customers of gmail and other email services are not offered repudiation as a feature.