Wouldn't it be worth providing some tools to assist admins in
checking/upgrading obsolete filters in their systems in one go, i.e.

- admin check
- external script / admin tool to run manually

Or do you reckon it's sufficient to let the automatic background update do
the job ?

I am not sure that process actually saves the converted/upgraded filters
back to the source (DB / Cookie). If not, then we definitely need to provide
a conversion process.