I don't consider that a failure at all.
From a business perspective, the Volt has been a failure at GM. They have lost money on it. If you are implying that they will parlay this failure into success in a growing market, then you are presuming that their simple presence in the market is their success. While there are a great many examples of business and product failures being credited with eventual successes, GM's prospects are not positive. GM does not have a strong record of learning lessons (that I am aware of). This story is about how GM seems to be going in the wrong direction with what they learned from the design, production and sales of their flagship product in the electric car market.
Currently there is not a very large market for electric cars. But it is undoubtedly growing and can be expected to do so. I don't know what % of that very small market GM has cornered. But there are both more economical products, more stylish products and higher performing products out there that are far outselling the Volt. The volt doesn't fill a demand or fit a niche. You have defined the success of the volt by it being their first venture into that area of the industry. This electric Caddy will be their second. Does that still make the Volt a success in your mind? Maybe only time will tell.
Compared to the history of the Tesla (which I thought I had made clear) in it's first several years into electric cars, yes, an overwhelming success......