I did think this may happen ... but I doubt it now. They are more likely to use their equity to help their children or continue to buy rental homes that first home buyers would want. i.e. a First home and a rental a very much the same.
I think what needs to happen is the baby boomers need to start dying for that change to come and then in those cases as well the children will inherit the houses and rentals - "landed gentry".
There is no quick fix to a housing shortage, that really needs 40,000-50,000 2-3 brm homes built a year to reduce the pent-up demand for Auckland and then 30,000 per year to maintain a status quo. Instead we are building 10,000-15,000 4-5 bdrm homes because that is where the biggest builder/developer profit comes from.