I personally have tried to get rid of all v4 hardware with the vSphere 5 release. It won't be supported in the next vSphere release, so the deadline is there. No issues with older Windows 2000/2003 and v8 that I have seen.
Brian Atkinson | vExpert | VMTN Moderator | Author of "VCP5-DCV VMware Certified Professional-Data Center Virtualization on vSphere 5.5 Study Guide: VCP-550" | @vmroyale | http://vmroyale.com