For the other specialty apparel retailers it will be net neutral. Gap is a big name in clothing retail but it doesn't offer a differentiated product and it is floundering against sharper competition at home. In fact its latest claim to product innovation is denim nostalgia ("Gap 69"). Wow, that's original. It sells the same kind of stuff as retailers like Just Jeans and its price points are slightly higher.
It will be interesting to see what kind of in-store experience the licensees contrive for Gap in Australia. Gap stores in the US are twice as large as the average Australian specialty store and this enables it to offer a clean look and good sightlines. One hopes that Gap doesn't get bundled into the kind of space that prevents it from putting its best foot forward from a branding standpoint.
If Gap turns out to be just the first of a wave of overseas brands to hit Australia as everyone expects then the biggest losers ultimately are going to be department stores, since the bulking up of the specialty sector will give people yet another excuse for avoiding them.