I hope not, since I find the Mach III one of the top razors around. I use it on and off with my Atra and I find these two to work fine for me.
I don't use the Mach III as much for my face as it's hard to get in close to detail my goatee, but it is great for my cleanup and touchups on the noggin. I have used it to shave my head a few times and it does work great.
I agree with Stu on the Atra handles, why do they not sell them anymore?, I am a big fan of Atra and it is my blade of choice for both my face and head.
I still have my handle from years back and I don't plan on getting rid of it, it has a great feel and a heft similar to a DE. I may have to check out ebay and see what they have. (I'm also one of those 5 Stu, lol.)
I haven't tried the jetables yet, but will have to pick some up next trip to Walgreens.
I've said this before and will say it again, I'm not a fan of the fusion, I think it's overkill and I remember saying years back, jokingly, what will Gillette do next, eight blades, ten blades?, they're almost there, how far can you go? lol.