I missed this on Thursday. It slipped out quite quietly. However, VMware have now released version 5.2.1 of vCloud Automation Center.
Possibly the best way to view this release is as an update-rollup as it includes features and fixes introduced in each of the following Hotfixes to 5.2:
Also included are a few changes that seem to me to be aimed at closing a few gaps between 5.2 and 6.0.
As far as upgrades go, the upgrade path seems to be from 5.2 only or 5.2.1 can be installed from scratch. There are a couple of installation / upgrade gotchas to be aware of so it's worth reading the release notes before planning an upgrade. I'll be giving it a try in the next few days.
It's not 100% clear if this will be the final release for vCAC in the 5.x branch. I'm thinking that it will very much depend on when VMware release a version of 6.x that supports upgrades from 5.x.