I'm sure that's what they're doing but when I called their support they weren't even aware of any firmware updates being pushed out. Weird. I had to call them because of this:
Saw Hamnats response about how he got the update (by changing the date)... thanks! I was able to get the update on my original s4. It DID fix the one display issue I was having, so hooray! The problem though was I initiated a warranty replacement because of 1) the display issue and 2) the SD card issue. After updating the original phone, I checked my mailbox at 9pm and the replacement phone was there.
Unfortunately changing the date (no matter how far) on the replacement wouldn't work. I would get software update interrupted your software is up to date. This was crucial to get as I noticed a secondary display issue involving the purple hue and blurring on grey screens while scrolling. I was able to get the update to work eventually but the patch did not fix that issue. It also turns out the original phone had the same secondary display problem and I just havent noticed it.
Also, Samsung Kies would NOT restore apps, ringtones, and perhaps an email setting... couldn't figure out why. Had to resort to using Helium which mostly worked.
Edit: Sorry for the long post. I did want to confirm changing the date did work for me on both phones, however had issues with the newer handset. I let the phone charge all the way for the second one and for some reason after waiting it worked. Just hope they don't release any more updates within the next month because by updating this way REALLY resets the time and you won't be able to update w/o forwarding time again.