I was sent a survey by VMware last week asking me for my opinions on the vSphere Enterprise Administration exam that will form part of the VCDX4 certification. I completed the survey as requested, and it definitely gives an insight into the content that will form the exam when it is released. The basis for the exam blueprint is clear from the various topics asked about in the survey. Jon Hall from VMware also created a post on the VCP community forum about the survey
I also listened to a 5-month old VMware Communties Roundtable recording (right-click to save the MP3) this week where Jon Hall was asked questions about VCDX4 (as well as VCP4 but that's all old news now). One of the things that Jon said that I hadn't heard before is that VCDX3 holders will only need to pass the vSphere Design exam in order to "upgrade" their certifications to VCDX4. Jon also said that the Enterprise Administration exam for vSphere would be available around now, I can't imagine we're that far away from seeing it - a few weeks perhaps.