CUCM 12.5 on VMWare on AWS is planned.   FCS target in Dec 2018.  

The only difference between a megacluster and a standard cluster is the number of subscribers.   There are no additional maintenance requirements.   Configuration is the same.   In order to leverage more than 10k configured devices per subscriber pai...

I am sorry this isn't documented well externally to Cisco.   Megaclusters are fully supported, but require a design review first.   You need to work with your Cisco Account team to submit the megalcuster for a design review.   I lead the team and cor...

Here is some details on the internal Cisco Megacluster page.   Megacluster OverviewBasic OverviewProvide support for customers that will exceed current advertised capacity of a cluster.Provide a Design review to see if cluster design will work with c...