i mean so many things could have happened, Benny would have the yes man, House wouldnt have anyone to aid him, The Brotherhood are without a savior or hero, The Legion stil has spies within the NCR and the NCR are still having problems up the ass... Ulyssus wouldnt seek revenge as the Courier is already dead
Im not sure how the world would've ended up had the Courier died.. personally i think we would have a 4-way stalemate but what do you think?