For the first time ever, the future of Google's mobile operating system will be determined by someone who isn't Andy Rubin.

Justin Sullivan / Getty Images Google's Andy Rubin unveils Android 3.0 Honeycomb at a press event at Google's headquarters on February 2, 2011

With Google‘s official blog, a peculiar but consistent rule prevails: the more boring the headline, the bigger the news. So when CEO Larry Page posts an item titled “Update from the CEO,” you can be pretty sure it’s not going to be a mere update from the CEO.

And it isn’t. Page’s blog post is an announcement that Andy Rubin is stepping down as head of Android to work on one or more other projects at Google. (Page doesn’t specify what Rubin will be up to except to say “Andy, more moonshots please!”) Longtime Googler Sundar Pichai, already responsible for Chrome, Chrome OS and apps such as Gmail and Google Calendar, will be adding Android to his portfolio.

Rubin co-founded Android as a startup in 2003, sold it to Google in 2005 and has run the business ever since. It’s safe to say that it reflects his vision, and we don’t really know what direction Android might take under someone else’s guidance.

The switch comes at an interesting time for the operating system. On one hand, it’s one of the biggest blockbusters that Google or any other tech company has had — according to IDC, an amazing 70% of smartphones shipped in the last quarter of 2012 ran Android. As Page notes, 750 million devices have been activated to date.

But that doesn’t mean that Google has figured out an Android business model that works. Most of the companies which make Android phones are losing money — except for Samsung, which is doing so well with its Galaxy products that it’s at least as important to the Android ecosystem as Google is. Android remains fractured into multiple versions, and new versions of the operating system reach consumers at an agonizingly slow pace — factors which help explain why Apple‘s iOS is a far more vibrant software and web platform even though there are more Android devices out there.

Meanwhile, if Google has figured out what to do with its own hardware division, Motorola, it hasn’t yet articulated a clear vision to us outsiders or released any landmark phones or tablets. Nor do we know how Samsung and other Google partners would react if Google tried to achieve Apple-like smoothness by seriously integrating its software and Motorola hardware. (Right now, it keeps other Android device manufacturers happy by teaming with them for Nexus devices such as the Nexus 4.)

I’m just a simple tech journalist, but it seems to me that Android isn’t going to continue to thrive through pure momentum; if it’s still successful two or three years from now, it’ll be because Google smartly adjusted its strategy rather than pursing an even-more-of-the-same approach.

Pichai’s great accomplishment at Google to date is Chrome, which came along at a time when it wasn’t clear that the world needed a new web browser — and then became an enormous hit mostly by being really, really good. Chrome OS, the operating system he already heads up, is an intriguing and inventive product, but it’s unclear whether Google will ever be able to convince many real people that they want it.

Now Pichai is in charge of an operating system that hundreds of millions of people want and use. Presumably, he got his new gig in part by giving Larry Page a crisp, ambitious game plan for the future of Android. It’ll be fascinating to see the results — and to hear what Pichai has to say at Google’s I/O developer conference in a couple of months.