there is no impact when you delete dvsData after moving all vms out of this datastore or after unregister all vms located in this datastore
Here is the explanation on why dvsData is created.
The .dvsData folder and the subfolder are primarily used for VMware High Availability (HA) when working with a vNetwork Distributed Switch (vDS).
When the virtual machine is using a dvport on the vDS, the ESX/ESXi host periodically syncs the port state into a file in a .dvsDatasubfolder on the same datastore on which the virtual machine resides (that is, where the .vmx file is located). When a VMware HA event occurs and the virtual machine tries to power on a different ESX host, the destination host reads the dvPort state from that subfolder and starts the virtual machine on that datastore.
When performing VMFS maintenance, ensure that no virtual machines on this datastore are registered in vCenter. After you do this, you can safely remove the .dvsData folder and subfolders.