Could be something that is sold bundled together with Di2 and a powermeter that you can either have or not depending on mood; kind of built into the system. That works for me...I wouldn't want it on all the time and I wouldn't want it adding any weight or mechanical complexity.
You nailed the signature feature. Ride it in automatic for general riding and override to manual when in the battle. Just software...no weight penalty.
Power meter hub or otherwise that will interface with the system will continue to come down in price as demand increases for the auto shift feature.
The future of Di2 without a doubt and the true benefit of electric shifting. Shift manual or leave in auto for general riding. Further this is the stone age. Algorithms and sensors will be further refined and auto shifting will likely be intuitive in the new 10 years.