With new gpgrt-config and *.pc files, *-config invocation can be now replaced by gpgrt-config invocation. This has done in new *.m4 scripts.
But we can't remove *-config script. Since there are still old software which invokes *-config script in configure script (from *.m4), we should keep offering *-config scripts, for some forthcoming years.
Yet, there can be some more improvements for *-config scripts. That is:
By improving gpg-error-config script (automatically detects the place for --libdir and also detects corresponding *.pc by its script name), gpg-error-config script can be the one which invokes gpgrt-config script with --libdir option and name for *.pc.
Then, all *-config script can be linked to gpg-error-config script.
See T4239: Should gpgrt-config have default LIBDIR definition in the script? for the gpgrt-config.