Given there’s a lot of interest at the moment in migrating off ESXi to other virtualization platforms, I’ve seen some tooling recently to do that for Cloudstack and Proxmox. Any plans to do something similar for Incus?
Plans, yes, time to implement them, not so much, at least yet 
For now, you can kinda do it by hand by getting the vmdk, converting to a raw image and use incus-migrate on that. But a proper migration tool would understand how to login to vCenter/ESXi, inspect the VM over the API, support multi stage data transfer and support booting into some kind of post-migrate environment that can inject the needed drivers (mostly relevant for Windows VMs).