Verizon has managed to alienate the 1% again. They snuck out an update which not only unroots your Galaxy S4, but also replaces your bootloader with a much more secure bootloader. The new bootloader takes away the old root method. It will not allow you to flash the prerelease kernel or any kernel at all. It also prevents you from even downgrading your bootloader to the original VRUAMDK firmware. If you have already taken this update you are out of luck for now.
There is a glimmer of hope. A thread over at XDA right now is offering a growing bounty for anyone who can either unlock the bootloader of the Galaxy S4, or root the device with the new firmware. Generally developers will release exploits and root methods free of charge with absolutely no expectation of anything in return. Hopefully the bounty will motivate a few security experts who wouldn't normally work on a root method to jump in and find the exploit that is needed.
It just doesn't seem fair for Verizon and Samsung to snatch Root right out from under us. Many of us actually need root to use some of the apps that we have paid for. Check out the bounty thread at the link below. I have already pledged $10.