The ARU is fine with ANZ being the premier stadium as they only want to play Bledisloes there, and any potential future World Cup finals. They've already moved all non-Bledisloe internationals back to Moore Park. There will be no objection on their part.
It does pose an interesting question as to where the big matches will be during the re-build. Origin will almost certainly revert to Allianz, but the Grand Final? Suncorp seems obvious - I'm not so sure. The Victorian government has never seen a sporting event that they don't want to steal from another state. If they offer big cash to take the GF to the MCG for a year or two and if they offer to fund a week of festivities like they AFL have then it will be hard for the NRL to say no.