How so? The only way in which the App Store doesn't support paid upgrades is that you can't offer a discount for existing users, and the new version needs to be

How so? The only way in which the App Store doesn't support paid upgrades is that you can't offer a discount for existing users, and the new version needs to be a separate app. But Halide 2 isn't any cheaper for existing customers anyway (there's just a launch discount).