Sony has announced it's latest Full-Frame FE Mount Lens, and with this range of 28-135mm this could be a great all around lens for video use. Although it's widest aperture is F/4 I don't think Sony A7s owners will have any issues with losing a few stops of light, if you can get over the price of $2499.
Sony FE PZ 28-135mm Lens
Designed for the demands of 4K and HD movie-making and high-resolution still photography, this weather-sealed full-frame E-mount lens features variable-speed zoom, powered by a Super Sonic wave Motor, along with quiet linear motor-driven autofocus and iris adjustment. Lens breathing during focusing and axial displacement while zooming has been reduced and there are independent control rings for zoom, focus, and iris, engineered to provide the right amount of torque for responsive operation. Optical SteadyShot image stabilization controls blur, while aspherical and ED lens elements, along with a Nano AR coating, provide sharp imaging devoid of flare and ghosting.