While vSphere 4.1 is not out yet, there are numerous leaks and announcements on the forums and other blogs on what to expect in 4.1
A partial list of features expected include:
1. ESX and ESXi direct support for Microsoft Active Directory through Likewise technology
2. Memory Compression for even higher VM density per host.
3. Scripted installations for ESXi making large rapid deployments supported and quick.
4. Storage I/O Control – Think of this is shares and limits for storage I/O to make sure important VMs get priority.
5. DRS VM Affinity – Restrict VM placement to particular hosts inside of an ESX cluster.
6. New HA dashboard for monitoring your ESX HA cluster.
7. Up to 8 simultaneous VMotions.
8. Microsoft Volume Shadow Service (VSS) in Windows Server 2008 and 2008 R2 guest operating systems for VADP
9. QoS engine that can prioritize between virtual machines, vMotion, Fault Tolerance (FT) and IP storage traffic.
10. Support for USB pass-through
Should be a very nice release!