Now that 4.4 is official on Sprint, it is safe to release this...
This zip is flashable via stock recovery to update to 4.4. Please note: I am NOT RESPONSIBLE for ANY damage caused to your device for using this zip. Proceed with caution.
Sprint 4.4 Flashable Update
If you have rooted or unlocked the bootloader previously, you will have to revert to stock firmware before flashing this. If you have never modified your system, you should be able to flash this with the method below.
To flash it:
0) Save zip in sdcard.
1) Shut off the device.
2) Power on holding the Volume Up + Power for about 15 seconds.
3) Release both buttons.
4) Press Volume Down in the bootloader until you have Recovery selected.
5) Press Volume Up to boot into recovery.
6) Recovery will say something about no command. This is normal. Press and hold Volume Up + Power for about 10 seconds.
7) Release both buttons.
8) You will now have the option to flash zip from sdcard. Locate the zip and flash.
Also, this is a full system dump with boot.img attached.
Sprint 4.4 Dump
Updated on 10-17.
Here is a new dump of the latest firmware 139.14.1.
Camera Update Dump