Can I hope that Lancelot will appear in Plasma5 soon? I am a big fan of Lancelot and very disappointed not to find it in the VM Kubuntu 15.04 Plasma 5.2.2 I am trying out

Unfortunately, it will not happen soon.

If Kubuntu has the old plasma libraries as well, you can use old lancelot in new plasma - just create an icon that will call qdbus org.kde.lancelot /Lancelot show 0 0