A Sponge plugin called Pore is currently indev. It should allow many Bukkit (non-net.minecraft source using code) plugins to work in a Sponge server.
This can be done by a 3rd party, and certainly will. I’m assuming you mean a web panel or GUI.
Probably not going to happen unless a plugin that has its own plugins (such as the Skript plugin on Bukkit) is made. Actually that’s something that I want to either make myself or seen made.
No, this is an API. It’s essentially a bare-bone server that other developers can make mods (plugins) to.
GOTO 2
As for tutorials, we need someone to do ‘official’ ones in order to clear any confusion from the start and to prevent a bunch of ten year olds from misguiding the community because they figured out how to use iMovie/Windows Movie Maker.
Swap and go plugins are not going to happen. It is very unsafe for plugins that hook in with databases (especially ebean) or plugins that rely on dependencies to be dynamically loaded and unloaded into the server. The safest and smartest thing to do when changing any jar file is a full restart. There are things like plugman which helps but is still mostly unsafe.