[X-Istence]

That is something that is listed for 9.3. You can have a M1 with R1, R2, R3.

Now you change R1 to master, and take M1 "offline", afterwards turn M1 back on, and have it become a slave to R1.

See http://wiki.postgresql.org/wiki/What's_new_in_PostgreSQL_9.3...