i dont think its something you should worry about, apple isnt going through this promotion and making an app just to "screw you over", in which case we arent paying anything so they arent screwing us over.
i'd assume it would take 24-48 hours to process it since everyone else who has the i4 is getting the app and ordering a case as well.
Thank god my email finally came. I was running around pulling my hair out at the thought of finding out a few days from now that my order didnt go through and I'd have to order again and have the case arrive at the same exact time as every one else that ordered within 5 minutes of the app being released!!!! AHHGHGHGHGH!!