VNX based replication sessions will not be migrated with its parent VDM/NAS server, no.

If you want to replicate the NAS servers once they are moved to Unity, this needs to be setup on the Unity side entirely after the migrations are completed.

Have a look at the migration doc for more info:

https://support.emc.com/docu71631_Dell-EMC-Unity:-Migration-Technologies---A-Detailed-Review.pdf?language=en_US