I was trying to answer your question concerning what we would do if/when the original game finally has a plugin API. 
Mojang gives the impression that its release is so far away that it isn’t even really a concern… people need a replacement for Bukkit, and Sponge can be that replacement for a long enough time that it’s not a worry.
If the ultimate release of the plugin API is any good, there should not be much difficulty in transitioning from Sponge. Even then, there may be some low-level API that Mojang will be unwilling to provide that Sponge can.
I get the point of your original post, and the reason there isn’t much of an official presentation is because the project has just started. The project’s organization and official stance is still being determined. What the public has now is information from the links in this reddit (primarily the Sponge FAQ) and the latest status update. For a week old project, it will have to do.