Christian Hesse [off-list ref] writes:
However... Even if GnuPG 2.2.x (or whatever future release) will become next
stable: It will not reintroduce support for rfc1991.
How certain are we about the deprecation?
It also would make us feel safer if we did not have to depend on the
version or keyfile format (which would not have anything to do with
the decision to support or not to support rfc1991 format) to check
if the feature is supported, but that is a separate issue.