VMware has announced it will finally not be releasing a thick client (C# client) for the next version of vSphere. The last few releases have lacked new features for the aging thick-client, while new features were added to the web client. It was only a matter of time before it was finally retired.
Fear not: the HTML5 web client will be fully-featured come release time. Grab and test the current HTML5 Web Client VMware Fling in your lab to help improve the HTML5 client before release:
The next version details like version numbers (6.1? 6.5? 7?) and release date are still unknown.