CUCM in this scenario is only used for Call Control for the video endpoints. In short, you simply are moving the video endpoints from registering to the VCS-C over to CUCM. If you are still looking to deploy B-2-B video, MRA and Hybrid Services for Spark, you still need the VCSC/E.
Take a look at this link.. https://www.cisco.com/c/en/us/td/docs/solutions/CVD/Collaboration/enterprise/collbcvd/edge.html
My recommendation is to migrate all video endpoints from the VCS to CUCM. Migrate the VCS-C/E to Virtual VCS-C/E as this will still be needed to allow traffic from inside to outside and vice versa that is if you are needing B2B capabilities. If you are running Cisco Jabber and need IM/Presence capability without VPN, you will need the VCSC/E (Expressway) servers anyways. Again if you are running the hardware version, then migrate to the Virtual appliances.
As for MCU it depends on how you were using the MCU. Cisco Meeting Server is the replacement for this. Another option is Cisco Webex/CMR/Spark or even a provider that offers VaaS such as Interoute.
It is best to look at all the options, compare and choose what best fits your companies needs.
If you plan on doing any B2B calling, or using MRA for registering endpoints or Jabber outside of your organization, your VCS-C/E can be used for this. The guides reference Expressway, but VCS can be used as well, since they're both running the same software, only difference is how they're incensed.
As Kelvin suggests, your MCU can be replaced with Cisco Meeting Server as it's the recommend on-premise conferencing solution, however you can rely on WebEx or Spark in the cloud for this as well. It all depends on your use case, how people will connect, total number of participants, etc.