The rumor is spreading that ESX 4.0 will be announced at VMWorld 2008 in Las Vegas. In the VMworld forum someone noticed that Lab A (Datacenter Tech Preview) is not available on Monday but starts right after the General session on Tuesday. You might conclude that ESX 4.0 will be announced during the general session on Tuesday. If you read the description of Lab A you can pretty much guess that this is about ESX 4.0:

LAB A description:

The next generation virtual datacenter from VMware will encompass exciting new technologies that further extend the flexibility, efficiency and dynamism of IT environments. A preview of these new server, networking and storage related technologies, how they work and how they can be configured to deliver higher levels of availability, resource efficiency and simplified management in IT environments will be provided.

It is pretty cool that we can get hands-on experience with the latest beta-product. Maybe we all get a USB-key with ESXi 4.0 beta?

There are also some other session that gives away that ESX 4.0 will be announced.