well one problem they have is zotac's zbox the newest one has the i7 3770t chip
http://www.zotacusa.com/zbox-id90.html
same size as the current mini and it has a better quad core then the 2012 mini. as for smaller the intel nuc has over heating issues as does the gigabyte brix.
I would be quite happy with a quad i7 4850 just have to wait.
I'd like to see a Mini with that i7-4850HQ too, the Zotac is currently unpriced so we don't know what value for money it is. The low power desktop chip would never be used in a Macbook Pro so it's hard to see Apple plumping for the Haswell equivalent i7-4770T.
What we could say is that thanks to Tim Cook's supply chain expertise we can see that parts for the Mini come out of various Macbook Pro parts bins. If the classic Macbook Pros are in danger I doubt that Apple would want to use such low order parts specifically for a Mini. It's more likely they would plan to use something that's going in a Retina model and in my view those are likely to value GPU over a little more CPU grunt and latterly less cpu power, smaller size and quiet over powerful, big and noisy.
See the new Haswell Macbook Airs for an example - they have gone from 17w CPUs to 15w CPUs, from 1.7GHz to 1.3GHz but in return have gone from HD4000 to HD5000 graphics. There could be a significantly thinner MBA when Broadwell comes round if, as mentioned elsewhere, they didn't have time to tinker with the MBA case for Haswell because they wanted to show something off at WWDC.
The improved graphics chips are, in my view, there to make sure of good display performance on 4k displays which surely can't be far off whether Apple make one or a 3rd party 4k monitor ends up on the market.
This is how I conclude that the Retina Macbook Pro 13 is going to provide the basis for the dual core Minis going forward but it's harder to conclude what the plan is for any quad core Mini given that the 15" cMBP could be axed in the next round of updates and there's a bit of a question mark over whether Apple would axe a discrete GPU such as the NVidia GT750m to make a thinner Retina Macbook Pro 15" using an i7 quad with Iris Pro 5200 at the expense of gaming and ultimate Photoshop CUDA performance.
If there is a prospect of the classic Macbook Pro 15" surviving it could mean that the case itself is going to continue to support a discrete GPU such as the NVidia GT750m and the classic model would live on with a TN screen as it does now.
The question then is what CPU/onboard GPU combination would they pair with the classic MBP that would then get used in the Mini. Yes, we'd love an Iris Pro 5200 capable CPU but I think Apple would be silly to cripple a quad core i7 with HD4600 graphics when the potential dual core Mini could come with a CPU that carries HD5100 graphics.
Finally, the fact that a Mini might have to cope with a 47w cpu option alongside a 28w cpu option leads to a bit of a logic leap in which Apple drop the quad core Mini entirely so they can design an even smaller Mini with a lower thermal profile, rather than keep the bigger case going. Could Apple produce a cheap enough quad core Mac Pro to fill the gap above a dual core Mini?