Overall propulsion package:
The current in-line series packaging of the 4-cylinder engine, the two electric motors and the multiple planetary clutches was a heavily patented revolution in the automotive industry, and remains light-years ahead of the competition. It could change, but at a bare minimum the arrangement may have been simplified for cost, size and weight savings.
This is a biggie -- both in terms of cost and potential. The current battery is 16.5 kW. Maximum U.S. tax savings -- $7,500 federal tax credit -- are reached at 16 kW. Therefore, expect the new battery to be 16 kW. However, the composition of the chemistry, as well the cooling and heating, will most likely have changed -- perhaps dramatically.
The current battery is a T-shaped one, which prevents a middle passenger in the back. That's a huge drawback. For this reason, GM would certainly have an incentive to find a way around it. Perhaps split up the battery into two more distinct parts, or do whatever else is necessary to make this a five-person car instead of a four-person car. It does not look like GM will take the approach of many other electric cars and make the batteries a part of a thin/flat floor.
This follows from the battery and is the biggest biggie of them all. The cost of manufacturing Volt 2.0 will be thousands of dollars lower than the current Volt. Most likely, the biggest contributor here will be a less-expensive battery, despite improved battery performance.
Despite falling cost, don't expect the price of the Volt to fall by much. Perhaps $1,000 -- perhaps nothing. The new car will be better, and GM needs the margins to improve.
One of the complaints of the Volt has been the four-way heat exchanger does not yield enough heat or A/C to make all four occupants happy. Expect major improvement here.
Volt 1.0 has a very busy interior, with too many creases, shapes and folds of really cheap plastics. Expect a major upgrade to this situation, which may even reduce cost given the complexity of the Volt 1.0 dashboard.