I've never heard of any rumors regarding an update to the EF 24-105mm f/4L IS USM.

Keep in mind, even if an update were released, it doesn't make the original model useless. The EF 24-105mm f/4L IS USM is an extremely useful general purpose lens. It's a lens I use surprisingly often even though I have many other lenses to choose from. And considering its grey market price (a little more than half of MSRP), it's a real bargain.