I just committed changes to allow make replace to deal with package
renaming (e.g., GConf2 -> GConf).  This was discussed a few months ago
and an earlier attempt backed out due to problems.

An example:

  cd /usr/pkgsrc/devel/GConf
  make replace OLDNAME=GConf2

will build GConf and remove the installed GConf2 package, moving the
+REQUIRED-BY file to the new GConf.  make replace behavior without
+OLDNAME should be unchanged.

I have tested this as well as I can on NetBSD-current, and I don't think
I added anything nonportable.  I would apprecciate review, particularly
variable quoting issues.

I am working on enhancing pkg_rolling-replace to use this feature to
handle renamed packages, but that will take a while because I think it
requires converting the internals from PKGBASE to PKGPATH.