Are both arrays in the same data center and/or on the same iSCSI subnet? I ask because if the hosts don't have connectivity to the iSCSI subnet on the replica side, they would never see the replicas once the VolColl is promoted.
Outside of this, I agree with Paul that it wouldn't hurt to engage Support to ensure that there are no gotchas in your plan.
I've done this several times, all without issue. I had the same reservations you do.
Promoting the volcol does not grant iSCSI access to the volumes. The volumes may even remain offline if I recall correctly.
1. promote volume collection. I think volumes remain offline, if not offline them. Then wait for a while before step 2. No sense in rushing this.
2. delete volumes
3. delete volcol
If by some chance a rescan was done of storage (assuming VMware) and it miraculously had access, VMware would see the same disk identifier and would not bring them online. They may appear in the list of datastores with _snapshot appended to the end.
When you promote the volume collection on the downstream array the volumes in that collection do become first class volumes and they do immediately go online. However, there is no access to the volumes via initiator group or chap. See attached. NOS 2.1.4, downstream array, promote volcollection, verify online, notice the access. So even if somebody rescind, the volume would not been seen.