Metaverse
I've always like the idea of some kind of "metaverse" standard protocol (we all know how well that goes) for seamless virtual worlds. Ever since playing MUDs in the early 90s the concept of being able to traverse worlds with a single "you" token would be cool.
For now I'll just have to amuse myself with the idea of a buff World of Warcraft character turning up in Minecraft only to have the world caught in the crossfire of a battle between Elite:Dangerous and Eve Online.
Anyone seen my dried frog pills?