VMware have advised that registration is now open for the VCAP5-DCA live lab exam.
Here's the official VCAP5-DCA page with links to the blueprint, a video demo of the user interface, and a list of testing centres where you can take the exam:
This is a vSphere 5 update to the VCAP4-DCA exam, and there are some changes to the vSphere features tested on in the exam - Ed Grigson did a great job of interpreting the exam blueprint (based on the beta exam) here so you don't have to:
VCAP5-DCA - What's New?
One additional thing that's been confirmed is that those who are already VCP4/VCAP4-DCA who pass the VCAP5-DCA exam until October 9th will also be awarded the VCP5 certification - after that date you will only be able to take VCAP5-DCA if you are already a VCP5.
In terms of preparation for the exam, well anyone that's taken the VCAP4-DCA exam will tell you to build a lab and practice, practice, practice!
There is an official instructor-led training class that aligns closely to the exam blueprint items - vSphere: Optimize and Scale [v5.0] - it is not mandatory to take the training but is an excellent class as well as giving you a chance to learn and practice the topics in the exam.