I agree that 50 MP isn’t necessarily too much, it depends entirely on the user. Probably at least 90% of photographers don’t need 50 MP though. Like @timtam said, the 5DS is probably aimed to lure people away from the medium format market. Although, if you really want a high end 50MP sensor, for only $8,496.95 you can get the Pentax 645Z, a modern CMOS medium format camera that is actually cheap, if you compare it to other medium format cameras, like Hasselblad’s H5D-50c which is also relatively new, with a 50MP CMOS sensor, only $27,500.00! And even as cheap as the Pentax is, it’s got better specs in most regards than the $30,000 one! The Pentax has a full-featured advanced auto focus system, the same one as it’s high end DSLR’s. Not to mention, it’s probably the only medium format camera in the world that has a tilting LCD screen.
So, @JamesStaddon, forget about upgrading to the 1D-X, just wait a few years till the Pentax 645Z is down to about $6,000… 🙂