The news was confirmed in a statement sent to Bloomberg via Musk's Boring Company, which said that it wants to "accelerate the development of this technology as fast as possible." That may pose an existential threat to the number of startups that have begun working on their Hyperloop designs. Businesses such as Hyperloop One, Hyperloop Transportation Technologies, Arrivo and TransPod have new competition.
The statement adds that Musk will continue to "encourage and support" everyone that wishes to build a Hyperloop. But, there is also a coded threat tacked on to the end, saying that these companies need to be "truthful," or face losing the use of the name. As SpaceX holds the Hyperloop trademark, it's possible that Musk could force companies he doesn't like to rebrand.
Last month, Musk tweeted that he had received informal approval to build his first Hyperloop, from NYC to DC -- approval that appears to have come from the White House. There are no concrete plans in place, but Musk's initial tweets prompted a flurry of chatter amongst the other Hyperloop companies. It was reasonable to assume that Boring Co. would dig the tunnels, with a partner building the loop itself.
What's not clear is why Musk has suddenly decided to reverse course and begin working on his own Hyperloop platform. It could be that the announcement is simply incentive to encourage others to speed up, although it's not as if things aren't moving at a pace. Hyperloop One just demonstrated its phase two test, and seems far closer to a finished product than anyone else. Not to mention, that unless SpaceX has been quietly developing a system, it is now several years behind these other companies.
But as well as SpaceX nurturing various academic pod design competitions, Musk has been a vocal backer of the Hyperloop project. Earlier today, in response to a negative story from The Guardian, Musk tweeted that "a proof of concept is needed." We just didn't realize that he was going to be the one to build it.