That’s up to the other distros. Kubuntu Focus paid specifically for supporting Plasma 6.6 branch which is used in Kubuntu 26.04 and which they will update as new bugfix releases are available (which will obviously be available to anyone).

Most distros either update to latest Plasma version or stay on whatever version wa scurrent when a given distro version was released (like Debian which doesn’t even update to new bugfix releases since it’s against their policy to do that. They backport only specific patches). So “LTS” as a concept is meaningless for them.