In the 19 months it has been on the market, over 5 million units of Google Cardboard have been shipped. That's a huge jump from last May when the company announced during Google I/O that it had shipped 1 million VR headsets. And those VR headsets are getting put to use, with over 350,000 hours of YouTube videos watched in VR, and 750,000 photos taken with the Cardboard Camera app Google launched last month.

Those numbers easily make Google Cardboard the most popular VR headset, but it is an entry level device, and that fact has left many wondering if Google would get involved with more serious hardware like Oculus, Valve, and Sony. Speaking to Time, Google VP of VR Clay Bavor said the best thing about Cardboard was that anyone with a smartphone could use it. "We think there’s something powerful and important in that," Bavor said, before hinting at the possibility of more powerful VR hardware in Google's future.

"Is that the end of the line? Of course it’s not the end of the line. I think if you imagine the types of things that a company with the ambition and the technical resources and the know-how of Google would be working on, we’re working on a lot of those things."