Anymore blades it'll start looking like the grill of an old Chevy Nova.
Hummm... 6 blades? Pretty soon the cartridge won't be able to handle any facial curves! 
I think the Fusion is already too bulky.
I'd be willing to give it a try.
I was looking at my FUSION yesterday and with the five blades there's room in there for another blade without enlarging/widening the basic cartridge. So the cartridge itself wouldn't be any wider/larger.
Nevertheless, the question remains......WHEREFORE DOST THOU DRAWETH THE LINE?
I dreweth the line at 3, Meister.
I think it's just overkill, and if you have facial hair there's no way you can get in close enough for detail work.
It's ridicurous, I say. lol