I very much doubt that. Of course someone might do it for kicks, but not for serious use; GPUs already have a task scheduler built into them, and compute cores

I very much doubt that. Of course someone might do it for kicks, but not for serious use; GPUs already have a task scheduler built into them, and compute cores don't like branching code - less so if it only needs a couple cores, like a general-purpose OS. There is little reason to waste them (and compromise efficiency) for Linux or any other OS.