Pampero project is divided in a few phases. In phase one both the server and connection managers will still be using blocking connections. That means that there is going to be a thread for each socket connection. Even with this architecture each JVM will be able to handle 5K-6K connections. So if you have 4 connection managers then you will have around 20-24K concurrent users in the main server.
Wildfire 3.0 will also include experimental support for non-blocking connections. Once we have a matured non-blocking solution we will change the main server and the connection managers to start using non-blocking connections. When using non-blocking connections each JVM should be able to handle several tens of thousands of connections without affecting the JVM performance.
The final stage of Wildfire is to have a layer of connection managers on top of a cluster of main servers. This architecture should let us scale up to the sky. Our intention is to reach this stage in 2006.