Google has some idea of what Chrome OS is supposed to be and what it targets, but it's not afraid to go outside those boundaries.
Chrome OS has had the most success when paired with a cheap, light and quiet laptop, the Samsung Chromebook for example, but Google is also pushing the Chromebook Pixel, at the very opposite end of the laptop spectrum.
It's not done though. One of the latest additions to Chrome OS is support for a docked mode. Specifically, it's now easier to use a Chromebook with an external monitor, keyboard and mouse.
If you close the laptop lid and you have an external monitor hooked up, Chrome OS won't go into suspended mode, though the laptop's screen will be powered down.
At the same time, Google is also working on adding a virtual keyboard to Chrome OS. Granted, Google has toyed around with the idea from the very beginning, but there's now a virtual keyboard to play around with, as long as you have a Chromebook Pixel, the only one with touch support. The virtual keyboard is hidden behind the "Virtual Keyboard" flag in chrome://flags.
All in all, this shows that Google is still thinking of expanding Chrome OS to more form factors, tablets or hybrids, for example.