Microsoft hasn't officially announced Xbox One sales numbers since January of this year, but a now-removed line in a recent Xbox Wire blog post previously indicated that the platform-holder has sold-through at least five million units since the console's launch in November 2013.
As spotted by Gamespot, the line originally read: "To date, five million Xbox One gamers have created more than 500 million clips…" Following the discovery, the line has since been changed. In its place is a more general line that reads, "To date, millions of Xbox One gamers have created more than 500 million clips…"
In a statement to GameSpot, David Dennis of Xbox Platform Communications explained, "The five million gamers referenced in the blog posting was related to the number of gamers that have used Upload and posted a video of their gameplay on Xbox One." As the site points out, it's not improbable that at least five million Xbox One consoles have been sold to date, but it's also possible that the number could be inflated should someone with an Xbox LIVE account have used a friend's system.
Seeing as how three million units were sold through the end of 2013, I'm willing to wager that Microsoft has sold at least two million additional units through 2014. In April, Microsoft announced that it had shipped (aka sold-in) five million Xbox One units, but this figure only represents units sold to retailers and not necessarily sold through to consumers. Comparitively, Sony announced last week during Gamescom that it had sold more than 10 million PS4 units worldwide as of August 10.
