It's pretty much all explained in the thread you linked.
An IRC log with questions and answers can be found here:
WowAce's Plans for the Future
It's basically gonna be the end of the wowaceupdater, and in the future you get your ace addons from the Curse Client (which will be redone). Alpha releases won't be available from the client, but beta and final releases will.
Basically it should result in more stable mods getting to the "end users", by keeping alpha stuff only the SVN only.
All mods from WoWAce will be found on the new site, even if they don't have an active author, so no mods will disappear.