That seems to be a change from how it worked in the past. While there was a small delay until the next sweep for status (twice monthly I believe), once it recognised you had attained a higher level the new status applies immediately - no waiting for a card.

I would guess NZ will send a card out early October and from then he will be able to use the gold status benefits.

NZ uses rolling 12 month status periods, thus the period is reset when a higher status is attained. Any unused silver complimentary status upgrades will be cancelled - so if possible use them up now.