I found some weeks ago this interesting infographic:
It tells us basically that VDI market is equally dominated by Citrix and VMware, each with about 40% market share.
From this data comes out an observation about projections of End of 2011: vmware is slowly but steadily eroding market shares from Citrix.
This trend can be explained looking at another data coming out of the research (realized by Morgan Stanley Alphawise): 68% of respondents use or plan to use vmware as their server virtualization vendor to support VDI. This value is almost 30 points above the market share of VMware View, and implies that several Citrix installations are based on VMware ESX rather than Xen.
The extended use of VMware inside datacenter thus is not affected by using other VDI software, rather is becoming a substantial driver for VMware VDI solution.