The stadium had more than 250,000 community users a year, including school events, and its function centre.
"We have an exciting couple of years of rugby and football coming up as we host the IRB Under-20s this year and the Fifa Under-20s in 2015.
"The stadium is in a fantastic condition - we have not stopped spending money on it - but the main field is used 11 times a year which is insufficient for our loyal paying patrons."
Mr Wijnstok said financial backing by the former North Shore City Council had freed the trust to establish a regional venue without crippling interest payments on loans.
The stadium has six artificial turf fields and a $20 million public swimming pool is being built next to it.
RFA director of stadiums, Doug Cole, said North Harbour would play a bigger role as the logical place for some of the games needing smaller seating capacity than Eden Park.
"It's got a good future."
In February, RFA took over Takapuna's Bruce Mason Centre which was $500,000 in debt.
North Harbour Stadium
1997 opening
$6m ratepayer grubstake
$45m replacement value in 2006
$60m valuation in 2014