I've seen MAME emulating everything available, but somehow those dance machines are left to oblivion. Techno Motion and the very first Andamiro hardware will be extinct sooner or later. I also still have hope for Konami Bemani System 573 Digital sound to work someday.
Now if I were to wish for not impossible wishes, that would be a skeleton N-Gage driver and the coming for more submissions to the project from new faces. I think emulation while commercially successful is becoming a lost art among new generations.
EDIT: And how could I forget about the first generation XBOX? I still have mine, but I hope for more improvements that bring it running, it doesn't matter if it's at 2 FPS.