Background
During Qubes OS summit 2024, it was revealed that parts of Qubes Air might come to r4.3, but sadly migration will not be a part of it.
For those who are not familiar with the concept of Qube (Virtual Machine) migration, it is a technology which allows transfer of Virtual Machines over network (Ethernet, WiFi, …) between two hypervisors (physical machines). This would eliminate requirement for backup/restore to/from spinning rust (old HDDs) or NAND (Flash drives and SSDs) for transferring qubes from an old computer to a new one. Which should be really convenient.
There are two kinds of migration:
Offline migration
This kind of migration requires you to turn off the VM. Only virtual volumes and some metadata is transferred between two machines.
Online migration
This technology does not require the VM to be turned off. Both hypervisors should emulate a similar CPU. Storage volumes and live changes to them could be gradually transferred over network; or they could be on some sort of clustered file-system, distributed storage (SAN, VMFS, Fiber-Channel, CephFS, GlusterFS, …). And the running VM memory is gradually transferred over network. This is a high-availability scenario which is only specific to server/cloud world. I am not aware of any Desktop OS capable of doing it.
Plans
While developing an on-line migration mechanism for Qubes OS is hypothetically possible, this is a very expensive technology to develop. This is what the big guys are spending a lot to have for their cloud servers (VMWare, Google, Amazon, …). So we could skip it.
Off-line migration is something which might be achievable in long term. This demands close monitoring of Qubes Air development and its capabilities to see if migration could be implemented on top of it.