Touchscreen video editing would be almost like taking us back to where it all began -- shuttling film back and forth under the cutter with our hands.
I like the idea of physical controllers with dedicated knobs and/or buttons per function. That isn't always practical though, since even users of the same software set it up differently and use different plugins. To keep size and cost under control, the designer has to decide which controls to leave out or bury under menus, so affordable devices tend not to be terribly useful while devices that do a good job of it (like the Digidesign D-Command) are priced an order of magnitude beyond my reach. Touchscreens seem like a really good compromise in that they provide the same kind of hands-on intuitive operation as a control surface but with infinite customizability and substantially lower cost.