I swapped emails with Jon Hall this evening, Jon is a Technical Certification Developer at VMware - in other words, he's the guys that writes the VCP and VCDX exams!
I asked Jon what the implications are on VCDX on the release of vSphere 4, and this was his reply:
"Just as we have announced a new exam and an upgrade path for existing VCP on VI3s who want to upgrade to VCP on vSphere 4, we intend to announce new exams and an upgrade path for the VCDX certification. As the VCP on vSphere 4 exam has just completed beta, it will be later this year before you could expect an Enterprise Administration on vSphere 4 Exam or a Design on vSphere 4 Exam. Only after those exams are available would we announce the upgrade path for existing VCDXs."
It's exactly what I was expecting to hear, but it's great to actually hear it.
I think the big questions is going to be "Is it worth doing the VCDX on VI3?" - well I think it is. To me, the VCDX is such a high-level certification for anyone to hold, that the version you hold it in is a lot less important than it is for the VCP.
It remains to be seen exactly what the upgrade process will be for VCDX, but if you compare it to other higher-level vendor certifications like MCSE (or MCITP as it is now) then some sort of single-exam upgrade process would be good to see.
Watch this space....