This addon, will automatically update your addons, from within the game itself, simply by storing the addons in your SavedVariables, loading them doing the addon loading process.
So how does this change anything? - It does, since you can update your SavedVariables ingame, so its simply a matter of updating those, which can be done, by the SkeenUpdater, by recieving an update ingame. - So addon developers, can simply push there addons onto curse, and even when a few people download it, they will automatically update other peoples addons, while playing in game. The addon updating process will be done while the client is mostly idle (hanging around in a major city, ect.)
So how about the issues? - One of the obvious issues, is that the addon being transfered might be only partly transfered, to avoid this, the updater will include a checksum calculator and checker, to simply make sure the data is ok.
As for the security of the update, then a system would have to be made up, likely along the lines of public-private key encryption of some sort, to ensure that people will be able trust the addon updates they're getting.