I was comparing some benchmark results the other night and I was amazed to find out the current 2.3GHz model is only slightly slower than the haswell 2.0 model (they both score over 12.000 in gb3). Now I don't know how big the difference is between the iris pro and hd 4000, but Cpu wise we won't see much difference. I'm wondering if Apple thinks this too and just decided to take things slowly, maybe until Broadwell arrives later this year.
At any rate, if there's no Haswell by april I'm seriously considering just to go with the current 2.3 i7 and call it a day. All i need is a smoother FCPX experience anyway, and fron what I understand the hd 4000 performs much better under it than my 320m.