Kubuntu and KDE are not really the same thing.
Just like Gnome KDE is a desktop environment (or as you called it, an interface) and is community developed/driven, it is not created by Canonical.
Kubuntu (and Mint KDE) is Ubuntu with KDE as an 'interface'. There are other OS's such as openSUSE that use KDE too.
Kubuntu was developed and supported by Canonical, but they have decided to drop it so they can concentrate their efforts on just Ubuntu and it's new interface called Unity (which is based on Gnome)......... yeah it gets a little confusing doesn't it!
As Viking says Kubuntu is now just developed by it's community with backing from Blue Systems, who also provide backing for Mint.
KDE is it's own thing, it's always been a standalone project so Canonical's decision to drop Kubuntu shouldn't affect it.
Sorry if I seemed to talk round in circles but hopefully that's answered your question....... but maybe created 10 more!