I think the CT6 is a hybrid because it uses more than one form of propulsion. According to early reports, it can operate on electric alone, but only up to 80 MPH, then it uses both. I suspect this is necessary to maintain a level of performance that is higher than the Volt.
The question is will the CT6 Plugin be based on the Volt. The Volt and Malibu are FWD. I would be surprised if it is not RWD same as the ICE versions. Although I think there will be an AWD option for the ICE versions. I see no reason why the general Voltec architecture can't be used in a RWD or even AWD via a traditional mechanical transfer case. Perhaps the bigger question is how the new Voltec transmission can be set up to handle a much more powerful ICE, I believe the 2 liter turbo will put out about 260 hp. Specifically, can the electric motors provide enough reactive torque in the two eCVT modes to handle the much higher torque.
In any case, no matter how the hybrid drive train works, I believe we will see variations of it in everything Cadillac makes. This is the direction BMW, Mercedes and other competing manufactures have said they will be doing. This will provide better economy, better performance, and more importantly, a more refined and quiet power delivery.