Well, not only is there no iris KL, there's no quad-core KL yet, either. Dual-core 15W CPU in a pro machine seems... inadequate. Also, all the 15" have dedicated graphics so an Iris Pro would seem like just a waste of TDP to me.
The IGP on the CPU is considerably more power efficient, the dedicated graphics can be pretty much switched of for anything non-Gaming or GPGPU related.
Yup. I'm just saving having (better, more power hungry) integrated graphics seems like a waste when you already have a dedicated GPU for when you want more performance.