He said whoever replaced him would bring a new perspective.
"Some fresh eyes, some fresh thinking ... whoever it is will be fresh. It will be for the enhancement of the legacy of the jersey," he said.
Hansen comes off contract with New Zealand Rugby (NZR) after the tournament, which runs next September and October.
He has been Head Coach of the All Blacks since 2012 and prior to that was an Assistant Coach for eight years.
Hansen told media this morning two big reasons for making the choice were what was right for the team, and what was right for his family.
"After being involved in the All Blacks for 16 years, I do feel it's right for the team for me to stand down. I think change after the Rugby World Cup will bring a new outlook for the team and it'll be time for someone else to enhance the legacy of the All Blacks."
He said he doesn't know what was next for him after he stepped down as coach but for now the focus was on winning the Rugby World Cup.
"Thankfully, I've been able to surround myself with good people and good players who have allowed me to make this decision myself. It's not the end because we've got another 12 months to go."
He wasn't reflecting just yet - now he had made the decision he was looking forward to the World Cup.
He said the potential for a third All Blacks win at the World Cup was "exciting".
"It is probably going to be the toughest World Cup ... from a competitive point of view."
Speaking about stepping down, Hansen said he wasn't sick of the pressure - he'd enjoyed it during his time as coach.
"I've been thinking about it for a long time. One of the things as a coach is to make sure you're doing the right thing for the team."
"I'd like to coach this team for the rest of my living days. But that's not the right thing to do.
"You can't do this job by yourself. Whilst I get a lot of the accolades, it's because of the people around [me]."