As always, we can't be certain what will go in and what won't; the project has strict quality standards that not all patches can make before deadline. All we can tell you is what's being worked on, which includes: synchronous replication, JSON support, security labels, nearest-neighbor geographic searches, SQL/MED external data connections, column-level collations, and index-only access. By the time 9.1 is released, though, this feature list will have changed considerably.