Yeah it's just a sketch, but the hood scoop does suggest that the WRX motor is under there. I don't think it makes sense to ship Saab engines all the way to Japan when Subaru has their own perfectly good ones right there. Also, the Impreza mounts its engines longitudinally with the transmission behind it like in a rwd application. It would take a lot of repackaging to fit an inline-four into the same location mounted the same way.