Unfortunately I see no evidence that this lens is real. Sure it would be nice to see, and I'm hopeful that Sigma is preparing to introduce more lenses like this, but this image proves nothing.
It is not a photograph. It is a software render of a 3D model. But that doesn't disprove the lens' existence: Sigma use renders like this as product images all the time.
But someone else could easily have created the model and rendered the image (using the same software?) to look like Sigma's images.
It would be an interesting lens option. Hopefully sharper than the EF 24-105/4 (and my experience with the Sigma GV lenses says that after calibration it probably would be). But at the same time bigger filters and increased weight (and possibly higher cost) would be negatives.
Like all these rumoured Sigma lenses, we'll have to wait and see. But fingers crossed!