I don't think it's being released right now due to some bad bugs.. It's the same update for all S4 phones I'm pretty sure and the ones that got it are having issues. Mine started to download I think but the "continue update" is greyed out. I read a 6 page thread about it yeasterday and I really don't think I want it till it's right.
I'm pretty sure AT&T are adding some propriatary code that is causing the issues cus other carriers aren't reporting any issues. You have to remember that AT&T phones are locked into their network so the software is probably "their" version.