It’s not coming soon
There are plans to release an EF 24-70 f/2.8L IS sometime in the next 18 months. I have confirmed from two sources that the end of 2013 or early 2014 is the earliest we’d see a production model announced.
There are no plans for a non-IS 24-70 f/4L.
Canon EF 24-70mm f/2.8L II USM Zoom Lens $2049 (Save $250)