That would be a great CPU to use, low cost too if Apple are ok with the HD 4600 graphics, but a redesign would be necessary as the resulting motherboard would have to be bigger to accommodate it. It's no bad thing if they have already decided to use a Mac Pro/Airport Express tall case style.
No other Apple product would use it unless they provide an upgrade to the
Early 2013 education model which is the only Ivy Bridge i3 model on sale.
If they wanted to provide higher power options for the middle range they'd have to design the case to cope with the 65W i5-4570S (which gains 2 more cores at the same 2.9GHz but loses hyperthreading for the same $192) or i5-4570R (which drops to 2.7GHz and 4 cores with no hyperthreading but gains Iris Pro 5200 Graphics at an unspecified higher cost).
At this stage, therefore, Apple may as well opt for having 4 genuine cores rather than a lower TDP for the same money if they are going to offer a mini in a case that has to cater for a 65W TDP processor.
The iMac 21.5" models are most likely to be i5-4570R in my opinion so Apple don't have to pay for additional discrete GPUs in that range.
The argument against desktop processors may end up being product differentiation. A truly headless iMac which doesn't use discrete graphics to all intents and purposes would cannibalise the iMac 21.5" on which it is based. Moreso if you could add your own RAM and perhaps even storage options. Imagine if someone could spec up a Mini with a desktop class i7-4770R and Fusion drive and bring their own monitor?
iMacs wouldn't be worth having for non gamers and any quad core entry level Mac Pro might be in danger too from those users who consider Iris Pro 5200 powerful enough and can bring an IPS screen of their choice.
This brings us back to a low cost entry level Mac Mini which would keep the HTPC and silent computing users happy. Perhaps Intel are about to show us some cheaper Haswell mobile chips in September which Apple will duly use in the entry level Mac Mini and perhaps in a Macbook Pro 13 non retina that's hanging on for another year? I'd be happy with a a 28w i5-4288U with Iris 5100 graphics even if that meant bumping up the base price by $117.
Perhaps people wanting a cheaper computer with a budget of $599 could be led towards the refreshed iPads with a bluetooth keyboard once iWork in the Cloud is launched?