Barcelona is going to be the first VCDX5 defenses, meaning you can submit a vSphere design and only be questioned on vSphere 5.x features. Sure with the current program you can submit vSphere 5 designs, but you will only receive a VCDX4 certification. So the real question what changes with VCDX 5?

The short answer is nothing. Nothing changes from all the blog posts and information that is out there for VCDX 5.