All of the 72-500 that I've been on recently have already had the cabin re-fit, which is just new seats to match the 72-600. The new seats are pretty good & even recline, but the general cabin also needs an refresh e.g wall panels and bulkheads.
Really wish they would install these seats on the Q300s as-well, as there seats are beyond horrible. Although I can see NZ adding an extra 20-25 ATR's (mix of 42/72-600s) to the fleet within the next 5 years see the Q300 leave.