Doubtless, Google is going mobile. But regardless of the rumors the Google Phone is about as likely as a Microsoft PC.
Building and selling a phone at the scale that a Google Phone would require is a lot of work and requires a huge infrastructure. Selling boxes with hardware in them is a completely different business than what Google is in at the moment. They might as well start selling breakfast cereals.
Building software (like an OS based on Linux), applications (like Gmail, Google Maps Mobile etc.) or search engines based on location or pattern recognition (the building blocks of the mobile internet) is another matter and much more likely for Google.
Then again, Microsoft does sell the Xbox, which is sort of like a Microsoft PC, so you never know…