Well hold on, LXD is a subset of LXC, that is LXC is at the heart of LXD but LXD brings with it a RESTful API written in Go to control LXC. Canonical doesn't own LXC, IBM wrote LXC.
LXD and LXC became really intertwined once Docker and CoreOS Containers dropped LXC and went their own way. Basically leaving LXD as the sole claim to fame for LXC. What Incus is doing is basically providing a RESTful API on top of LXC, pretty much the exact same way LXD does exactly that as well.
In fact given Canonical's Google-lite approach to dropping projects like they're hot and the maintainers that are heading to Incus, Incus is less fragmentation and more migration.
the initial set of maintainers for Incus will include Christian Brauner, Serge Hallyn, Stéphane Graber and Tycho Andersen
I mean that pretty much is the bulk of people that know how this software works inside and out. I just don't see Canonical (inventor of the MIR Display Server) devoting the resources to keeping up with LXD when a good bit of mind-share just moved over to Incus.
This is just more of the same that's helping Canonical become less leader in the deb based distros and more just a player. Add in their wonderful call to double down on snaps and you've got a 1-2 combo they've dealt to themselves. Canonical just did the MySQL vs MariaDB to LXD. Like MySQL is still useful, but MariaDB left MySQL in terms of features and functions in the dust long ago. You use MySQL today because of name recognition. You use MariaDB when you actually need a database with actual features.
And the likelihood the exact same thing happens with LXD just jumped an order of magnitude by seeing who just signed on to Incus.
EDIT: And Incus has replaced LXD on the linuxcontainers.org page already. Ooof. I wouldn't want to be Canonical at the moment.