The Lubuntu 16.04 desktop is using the GTK-based LXDE rather than LXQt, the new desktop written in Qt that merges the work of LXDE and Razor-qt. While LXQt has already seen some significant releases and is built atop Qt 5 and KDE Frameworks 5, it's not coming for Lubuntu 16.04.
Today's Lubuntu Xenial Alpha 1 release notes state, "LXQt is still in development, as such Xenial Xerus is GTK based." LXDE continues to be GTK2-based and is still under limited development.
If you want to easily try out LXQt, there are distributions like Mageia that are already shipping it. LXQt is also available for Arch Linux users. While not the default for Lubuntu or other Ubuntu derivatives, there are lxqt packages present in the Ubuntu Xenial archive for those wishing to install it after the fact.