My take, given the optics of the change:

Canonical is likely looking to bolster LXD integration within Ubuntu and drop support for other distros.

Which... is fair, in my opinion. They've done most of the maintenance and work, they are allowed to prioritize their use-cases.

But it also means there likely does need to be a fork available to make sure that wide distro support happens, and LXD doesn't become a snap store special for Ubuntu.

In the best case - They'll both cooperate nicely and canonical can focus on primary LXD development like they were, while other folks can pick up the tab for non-ubuntu packaging/testing/support.