I'm sure it's been asked a 5 billion trillion times before... i did try to do a simple forum search for linux. Who, when, and where? Seriously why isn't there parallels for linux? OSX is based on BSD and BSD is kind of sorta of related linux. It sure would be nice to run windows with the GPU acceleration Parallels has on mac but, on linux. Linux is ever so slowly gaining momentum, specially Valve on there holy crusade to really push for linux on gaming. These days you can included the requisite packages in the installer. If money or user interest is an issue you can always do a kickstarter to see if people are really interested.
Parallels had Parallels Workstation for Windows and Linux and discontinued in order to focus on running Windows on Macs, which is where they are better than the competition.
How many years ago was that? could it handle games like GTA IV like Parallels Desktop for Mac 9? With a successful kickstarter they could probably afford to hire a few extra hands/experts.