perhaps "the chosen one" is more of a long term effect type of thing and not just say killing palps or wiping out the jedi, its the total effect of everything he accomplished both as anakin and as vader and the lasting effects of those accomplishments that continued to play out even after he was dead including being the father of luke n leia.
say for instance if ani/vader never happened would yoda still have sought out the training to become force ghost and therefore teach obiwan how to as well and bring anakin into the fold. since the EU is null and void that trio is still "alive" and well in the force heaven and still capable of influencing current events and acheiving more
so what i'm saying as far as chosen one we got to look at the bigger picture
