Even if you could pick the day, testing the above hypothesis would be very hard. IF you could guess when the most iPhones would be bought, you couldn't possibly know when people would first visit the App Store (they might not go on the same day they buy the phone). Moreover, even if you got on the list of top apps for that day, it might not be as useful as having already been selling your app for a few days. To me, having known customers is more useful than waiting for the moment of the most potential customers. It sounds nice to be able to wait to launch on the best day and have a nice launch day, but I'd rather get out there sooner and build up my customer base, even if it's slow. In my view, unless you have an actual promotion planned, any day after your app is ready is too late.
