Leo,
The C4500x as a 10G switch needs a 40G uplink option to integrate into the new C9500 or other 40G core options.
We have several C4500x in closets, in distribution (1/10Gb) and core roles. As core moves to 40G, these distribution switches need a 40Gb uplink option. How many C4500x switches are out there, you cannot write of their need for 40G module.
I never viewed C4500x as comparable with the new C9400s. I matched them as alternatives for the C4507/4510 switches.
Aidan