since PostgreSQL 8.1 has just been released, I plan to remove 7.3 next
  week. Currently two packages depend on it, I'll have a look into those
  dependencies first.

Particularly with databases, I'd expect people to be cautious in
upgrading, and think it's good for pkgsrc to continue support the
latest stable version in a series until doing so causes some pain.
It's not clear to me why the release of 8.1 should trigger removal of
7.3, since I don't see how that gets us to "it would be totally
unreasonable for someone to want to build 7.3, even someone who has an
existing format X database that doesn't want to migrate it".  If the
answer is "anyone who thinkgs they want 7.3 is confused and should
just build 7.4 and won't have to do any migration work, even if they
have an existing 7.3.x installation", then 7.3 can be removed, even
without 8.1.

I'm not enough of a pg weenie to know the answers, and it wasn't clear
from your note.  So unless migration from 7.3 to 7.4 is as simple as

/etc/rc.d/pgsql stop
pkg_delete postgresql\*
cd /usr/pkgsrc/databases/postgresql-74 && make package clean
/etc/rc.d/pgsql start

(more or less, depending packages like guile-pg etc.)

then I think 7.3 should stay.  If it is that easy, then sure it can
go.




-- 
        Greg Troxel <gdt@ir.bbn.com>