There’s been rumors that VI 4.0 will be announced at vmworld 2008 in Las Vegas.
Some of the features you may see are Linked Clone, VMware CA (Continuous Availability), VCB 4.0 with Incremental & Differential, Chargeback, Improved Life Cycle Manager, ISO Manager, VMSafe, Virtual Center Clustering, Unified Network Management and more…
Some of these features were already demoed previously in vmworld 2007.
Virtualization.info has also posted a partial list of new features here.