It would work if you are fine with having downtime for your VM's.
If you cannot afford downtime,you can try install same set of ESX(i) version on few new set of servers( say 10 out of 50 new servers) and add them to Old VC and proceed with below steps
- Configure old NFS storage on new set of servers
- Migrate(vMotion) all the VM's on old NFS to new set of servers
- Remove all the new set of servers from VC
- Add same set of new servers(to which VM's were migrated) to new VC
-Migrate all the VM's to new storage and then upgrade your new set of servers
I feel this way you can avoid having a downtime for your VM's.