Upload & Sell: On
Without IS it would be pretty much an ordinary lens, regardless how much of an improvement the optical part would be. If Nikon felt necessary to put in a VR in their 16-35mm lens, it would be a major omission for Canon not to put in IS in a new 24-70mm lens, soon or later. Period.
Did Nikon put VR in their new 24-70Z? Did Sigma put OS in their new 24-70?
Maybe Canon could differentiate themselves, but Sigma is hardly taking huge number of sales from the to need to differentiate themselves. If it's as good of an improvement as the 70-200L mk II then it'll sell like hotcakes.