The chances of Hyperloop actually working are nearly 100 percent as the science as already been proved. The chances of Hyperloop becoming a constructed reality is an entirely different concern.
Technology. Most of the technology described in Musk's paper exists today, much of it practically off the shelf. The most basic and brief description of the Hyperloop is that it mimics the pneumatic tubes used in banks and large buildings to send mail and other goods short distances. Of course, this can't be achieved without a little innovation. Perhaps the most important of the solutions described in the whitepaper is how the Hyperloop . Musk writes,
The approach that I believe would overcome the Kantrowitz limit is to mount an electric compressor fan on the nose of the pod that actively transfers high pressure air from the front to the rear of the vessel. This is like having a pump in the head of the syringe actively relieving pressure.
Cost. The paper claims that the proposed system could be built entirely for less than 6 billion USD, and in his press conference Musk even further. This is a mere fraction (11.3 percent) of the cost of the project's Phase 1, which similarly links San Francisco with Los Angeles for a whopping $68 billion USD. The whitepaper Musk released also declares that "amortizing this capital cost over 20 years and adding daily operational costs gives a total of about $20 USD (in current year dollars) plus operating costs per one-way ticket on the passenger Hyperloop." Basically, the Hyperloop would not only be unbelievably inexpensive for a project of this scale but would pay itself back in 20 years, assuming a trip charge of just $20 -- one third the price of a plane ticket.
The technology exists, the capital exists, there's just a lot of paperwork to be done.