Actually we use docker from Ubuntu 20.04 as it was way newer than the version in Debian-10-Buster when UCS-5.0-0 was released. Nevertheless no (major) update is planned as they include incompatible changes, which might break other use-cases.
The next UCS will be based on Debian-12-Bookworm, which is scheduled for this summer. It will then contain an updated version of docker, too.