VCP4 has essentially been the "industry standard" virtualisation certification since it was first released back in 2009, and there are thousands of individuals who already hold the certification. I train people all the time who want to gain VCP4, but now VMware have launched vSphere 5 it won't be too long til VCP5 certification becomes available.
If you've yet to train on vSphere 4 and want to gain both VCP4 and VCP5 certifications, here's the path that you need to follow:
Note that from March 1st 2012, attendance of the vSphere 5: What's New course is no longer optional for a VCP4 to achieve VCP5.
VMware have already added a number of VCP5-related resources to their site, more information on that can be found on this blog post: New certification: VCP5