I think developers who don't want to give 30% are going to have to deal with a new enemy: Piracy. The moment sideloading is available for iPhone, I expect within weeks there will be a cool, first-of-its-kind piracy App Store. As well as, within months, a cool, first-of-its-kind hacked game clients for iOS App Store. I think Epic Games might quickly discover that 30% might be lost to Apple or Piracy, pick your poison.