Christchurch rebuild was derailed by a much bigger monster than our Govt, Insurance companies (and reinsurance companies) who clearly didn't understand their risk / liability over "total replacement" type policies where a 150sqm house built 30 years ago for a fiver, was now going to cost upwards of $200k (back before house building prices went really stupid), it was very difficult, if not downright impossible to actually put a number on a payout (and being insurance companies, they wanted to pay out the fiver and be done with it).
Replacement for JA, no one really springs to mind. Hipkins may be the obvious choice, but would he really want it? I think he is too smart to take on something 9 months out from an election where the party is taking a beating at every turn, but more importantly for elections its the economy that will dictate the winner (almost always does). Health, education and justice make for good headlines, but if the economy is still in the crapper (regardless of who is to blame), any incumbent Govt is more than likely on a hiding to nothing going into a general election. Hipkins will be well aware of this.