From my understanding, Earth is just a toolkit for building GUIs. AceGUI is intended for that. Sea is nothing I would "Ace" exactly. What we have instead is AceUtil which provides for sharing functions without the need to distribute a central library or force an additional dependency.
As for Sky, I'm sure a lot of people would appreciate that kind of capability, but from the sounds of things any such implementation will be a bit messy because the game system handling chat channels is very messy.
I can't say too much yet but Tem is working on an intercollaborative system between clients and there has been some brilliant implementation-work going on. It's not Sky at all or anything like it but something that uses a superiour approach and better ideas to create a system wherein proper throttling can occur and it won't lockup channels, either. Addons will even be able to assign their own importance going through this and Addon authors will be able to announce their importance level with their dependency note just so players know which areas of their transmission space are too occupied or not.
It's a completely different approach from Sky and uses none of the code that Sky has (because frankly; it's a buggy, squishy, icky mess of barely functional nonsense). Tem's decided on Satellite for the name, which is very apt (since mass-communications is usually something that satellites do and very well, at that).
This is definitely something that everyone should be looking forward too, though. The brilliance of folks like Tem goes over that of my own by leaps and bounds and they end up doing wonderful things with metatables that most folks wouldn't even try to conceive. It's basically going through the pain of coding as closely to Warcraft's Lua-core as possible to provide the most optimized solution you could imagine.