The iPad is not going to run Logic any time soon. It doesn't even run GarageBand. Apple is not positioning it as a professional device.
However, it would be an amazing Logic controller. I'd love to see it have some functionality in GarageBand, too.
It will happen within a few days. Controlling Logic that is. The iPad is not powerfull enough to run logic
Logic can be controlled by any MIDI control surface. All that is needed is for someone to write an app for the iPad. And guess what? Such an app is available today for iPhone. This is being ported to iPad. Should be available within days. Look here: