Die off? Honestly, I love IC2 and GT, but they hold a very small foothold in "mainstream" modding. MJ is slowly losing traction, yes but RF is probably going to be the new standard for mods not wanting to implement pwr gen of their own.
I don't know what's all the hate for buildcraft. Simple, understandable, usable, universal. I actually like it for the pipes, not for the quarries. Perfect for early-game automation.