Are you serious? I feel like it's the exact opposite with the 5DIII, the video was only slightly improved but the stills side was improved tremendously. It really is an amazing still camera, world's better than the 5DII.
I was gonna say the same. The "video improvements" on the 5DIII are basically you have a choice of codecs, and some better low-light handling, but, that is also a stills improvement anyway. On the stills side, you got better everything; AF, fps, low-light, the list goes on. Image quality isn't just a function of the sensor. The camera and lens can be as sharp as they want, with a crap AF system, your IQ sucks cause they are blurry. Likewise with the bump in fps.
And until we actually see the T4i, it's hard to say its just a "video update". Especially since the T3i was basically just a screen update compared to the T1i to T2i shift.