That is the ratio in resolution between the new (4.7 in) and last generation iPhones. That is a really ugly number, especially if you have pixel art in your game. It seems like a no brainer that Apple would keep the width a multiple of 320 (the width of the original iPhone). Transition from original iPhones to retina was relatively painless because retina images were exactly 2x the size of the original. This transition will be painful for devs. The 5.5 in iPhone complicates things even more. Not only does it not share a resolution common denominator with older devices, it doesn't even share a common denominator with the 4.7 in iPhone (ratio of resolution is 1.44 ??!?). This will drive devs away from using pixel art towards real time rendered art and maybe even SVG (although to my knowledge a good vector solution for iOS doesn't exist currently). Pain!
I think we need a good SVG solution.