Don't get us wrong; we've got no beef with enormously powerful luxury vehicles. In fact, we love 'em. But while Mercedes' AMG division has shoehorned their bestial power plants into all manner of vehicles big and small, BMW's Motorsport division has always drawn a line in the Bavarian sand. They'd tune the 3 Series and the 5 Series along with a handful of coupes and convertibles, but that's where it ended. But that line seems to be eroding, as spy shots of what could be an M7 sedan have been snapped soon after the news of M-tuned X5 and X6 crossovers.