Yes.

http://nodejs.org/api/events.html#events_emitter_emit_event_arg1_arg2 says: Execute each of the listeners in order with the supplied arguments.

http://nodejs.org/api/events.html#events_emitter_addlistener_event_listener (same as on):
Adds a listener to the end of the listeners array for the specified event. 

And the implementation explicitly uses a list and maintains the ordering (once it upgrades from a single listener).  Given the existing docs and that this is the historical implementation, it seems like there is a 0% chance of this changing.