I offer my wholehearted support for this motion
I think it would be brilliant if the KDE localisation project was moved to Translatewiki.net. The current website (which uses the KDE3 style, like almost all KDE sites unfortunately) presents a large barrier to most people including me, and I was not very enthusiastic about signing up for it.
But I've always been enthusiastic about quality software translations. As a full-time KDE user (with no other operating systems/desktop environments on my computer), I would be proud to improve the quality of the translation (it's fairly complete) for the Greek language, and I strongly believe that the KDE localisation project would grow massively were it hosted on Translatewiki.net. Additionally, KDE e.V. won't have to pay for the required infrastructure anymore.
So in conclusion, I think a migration to Translatewiki.net to handle KDE translations would be greatly beneficial to the KDE Software Compilation, KDE e.V. and the KDE users' community in just about every single way possible.
My only reserve is that developers of individual applications (e.g. KDE games developers) are sometimes cut off from the wider KDE ecosystem (e.g. a lot of Kontact developers also work on Akonadi)... they would need to be exposed to Translatewiki.net somehow and be willing to take translations from here and into their software projects. I'm confident something can be worked out, though. :)
I think the two databases could easily be synchronized, so that users can still contribute using Lokalize (or other .po editor) pulling/pushing messages directly to KDE servers.
Yes, the Translate extension export can handle that. When translation for MediaWiki started here, there were people still translating via direct commit, it wasn't an immediate complete switch.
Of course, it's easier for people to coordinate and collaborate if they use a single tool, so the general idea is to support only the languages whose teams want to use translatewiki.net, meaning that all of them want to move here and no conflicts happen.