We're told that the long rumored IS version of the EF 24-70mm f/2.8L is still in testing but has not yet been given an announcement date. There are apparently still two versions of the lens being developed, with only one coming to market.
Canon's goal is to make the new IS version of the lens noticeably better optically than the current EF 24-70mm f/2.8L II and just adding IS to the 6 year old optical formula. The second goal of the lens has been weight, adding image stabilization adds weight and bulk to a lens. Nikon's non-VR and VR versions of their 24-70mm f/2.8 has a weight difference of about 170 grams, which you can feel when shooting all day, the VR version is also noticeably bigger in size.
We were told back in 2012 that Canon had worked on an EF 24-70mm f/2.8L IS & EF 24-70mm f/4L IS alongside the EF 24-70mm f/2.8L II development, and as we know, chose to release the EF 24-70mm f/4L IS a few months after the current f/2.8 lens. Now keep in mind that L zooms take years to develop from start to finish and various prototypes will obviously exist.
Every other lens manufacturer seems to have an IS version of their 24-70mm f/2.8 version and Canon seems to pride itself on being the market leader in lens technology, so I think it's only a matter of time until we see an EF 24-70mm f/2.8L IS.
More to come…