PostgreSQL's next version was due to be 8.5, and the last 3 alpha releases have been labeled as such, but a decision has been made, announced yesterday morning, that due to the significant new features available in the next version, that it will now be released as version 9.0.
The new features in question are the combination of Hot Standby with Streaming Replication. This means PostgreSQL finally has true replication built natively into it's core without the need for additional software. Anyone who's previously looked into replication for PostgreSQL knows that the sheer number of replication options for PostgreSQL are mind-boggling, each one with their advantages and disadvantages. (examples are PgPool-II, Bucardo, Slony-I, PgCluster and Londiste)
Due to this decision, PostgreSQL is going from 8.5 alpha 3 to 9.0 alpha 4.
With MySQL's dubious future, and multi-forked projects, PostgreSQL really has a chance to become the open source RDBMS of choice, or merely just the RDBMS of choice. It's legendary stability, reliability, functionality, standards compliance and feature set now has the killer feature added to it, true replication.
But don't let this be your only distraction for the next release. There will also be Writable Common Table Expressions (with PostgreSQL being the only database to ever have such a thing), conditional triggers, column-level triggers, DO statements to execute PL code without the need for a function, and many more features.
This is definitely a release to watch out for.