There are almost three years since Google Drive launched and we have yet to see an official client for Linux. While there are various unofficial clients, none of them is perfect, with Insync probably being the best option, but it costs $15 per Google account and not everybody wants to pay for something Google is offering for free on Windows, Mac and mobile.
After such a long period of time, some may think that an official Google Drive Linux client is never going to be released, however there are a couple of screenshots which indicate otherwise:
The screenshots above are bundled with the official Google Drive Mac client and they first appeared with version 1.18.7821.2489 (I checked the previous version and some random old versions and none contained these screenshots), released on October 30, 2014, which isn't long ago and it most probably means that Google is testing Drive for Linux internally. So we might actually see an official release pretty soon.
Those who want to see this for themselves can download the latest Google Drive for Mac, mount it and look under Google Drive.app/Contents/Resources/lib/python2.7/resources/images/
We'll let you know if we find out more.
Thanks to Francisco!