that's the IATA code (which I didn't know myself until I checked this morning). I've always known it as WLG which is the navaids.
The navaids are all "WN" not WLG.
The reality is that if the WB machines don't arrive it will be Air NZ, QF and VA passengers that will have to pay for the extension that they don't need. Airport companies don't take a loss!
Given what lies at the end of that runway (a ten meter drop, trolley bus wires and a gas main), the extension will be useful even if it doesn't attract WB aircraft.
kiwiandrew Water wings is totally correct. All this would really do is make a currently unsafe airport safer for existing operations. In practical terms it won't provide much additional useable runway length.
Furthermore, even if additional runway was provided who exactly is going to use it? Long haul ops out of WLG are a pipe dream. CBR and WLG are similar sizes, but CBR is a couple of hours flying time close to most markets. If CBR can't justify longhaul ops I can't see how WLG could. ( Don't be fooled by the fact that CHC has some longhaul ops, it is the inbound gateway for longhaul tourists to the South Island - WLG would be an inbound gateway to what exactly? ... WLG and the Wairarapa vineyards? )
CHC is nothing more than a notional gateway to the South Island anyway, most travel via AKL then hop a jet south or increasingly for Australians, fly direct to ZQN.
And for some current and presumably most future types, Newlands ridge is no longer the performance impediment it used to be due to the availability of alternative single engine departure procedures.