In the case of Neon, piper is, for once, wrong. The devs there are setting up a repo (not connected to Ubuntu in any way) to place latest kde applications in (latest versions of course). This repo is not filled yet, so I have not tested this. It will probably work, but I guess it will not be an official way for siduction and will not be officialy supported. At least that is my take on it right now.
greetz
devil