Probably questions best asked on hackers but I figure many are represented here.
Will there ever be a release where a dump-restore is not necessary?
Perhaps, at least, minor releases (e.g. 9.0 to 9.1) will not require a
dump-restore?
From 9.0 Release Notes:
E.1.2. Migration to Version 9.0
A dump/restore using pg_dump, or use of pg_upgrade, is required for
those wishing to migrate data from any previous release.
Version 9.0 contains a number of changes that selectively break
backwards compatibility in order to support new features and code
quality improvements. Also, users who make extensive use of PL/pgSQL,
Point-In-Time Recovery (PITR), and Warm Standby should test their
solutions because of slight user-visible changes in these areas.