Different zip codes on the AT&T site all show shipping date as April 30th.
More than likely, which is why I never bother pre-ordering phones. It always seems like those that pre-order get it after those that casually walk in.
This is not true in the last two phones I preordered and had delivered from ATT. I had the S3 for a week or so before it was available in store and the note 2 the first day it was available. With that said I know it can be frustrating because ATT is so slow to release info to their customers on what is going on.
I like getting the phone, unboxing it myself, and then just popping my SIM in. No fuss, no muss no chance of messing up my unlimited data etc. which can all happen when the Reps go into you account...that is just me though.
My advice though this entire process is to be patient, ATT does not release information fast enough. If you call every day, you will get a different answer. Plan on the date on your confirmation email.
Good luck and enjoy your S4! Use this time to get a screen protector and initial case ordered! Lots of cases on Amazon already.