I just did the update to 2025-Q2 (I use the quarterly stream build).

Initially I thought this is going to be a huge pain. I have many interfaces and also pass-through hardware like the SFP28 card. I made a copy of my primary router vm and added fake interfaces with the same MAC addresses. I then went through the update procedure which was very simple.

in vyos vm:

  wget https://community-downloads.vyos.dev/stream/1.5-stream-2025-Q2/vyos-1.5-stream-2025-Q2-generic-amd64.iso -o vyos-1.5-stream-2025-Q2.iso
  add system image /mnt/iso/vyos-1.5-stream-2025-Q2.iso
  # follow prompts
  reboot
  # boot screen will offer two version now, old and new

That was it and it worked. So from now on I know I can just take a snapshot of my vm and do it directly on the main vm without making a copy.

You do loose any custom configs you may have. In my case it was fstab changes and my cron entries.