I recall seeing a recent interview with BG of Virgin Blue which hinted at Pac Blue getting IFE for trans Tasman - this could put pressure on NZ to have IFE on domestic.
Also having an all Y Domestic with IFE would suit putting these planes onto price sensitive leisure orientated Trans-Tasman routes such as Wgn/ChCh - OOL/BNE where the lower cost would be desirable when up against J* or Pac Blue.