postgresql roadmap for horizontal scalability?

Hi,

This database has exceeded all expectations and perhaps I am getting
ahead of myself but is there anything in the roadmap to match Oracles
ability to cluster databases across multiple servers for concurrent
access?

The reason I ask is for the architecture of an open source database
project I am working on.  It is tempting to ignore caching altogether
and push the onus on to the database to perform more database queries.
This is makes life easier and allows the focus to be on the business
logic.

However if Postgresql is the datababase and the only means to scale is
to buy a bigger single server then that could become a problem of cost
to the community.  It would be cheaper to scale across multiple smaller
servers (I think).

The application I am working on is OLTP with say 90% reads to writes
ratio.