It's worth pointing out that macOS Mojave makes it almost certain(tm) that the base 21.5" iMac will be going Retina 4k in the next refresh if you judge that 1080p (non retina) screens look poor on the new OS.
Perhaps that's a factor in whatever the Mini becomes specified as - if any iMac is obviously better value for money than a Mac Mini come the 2018 refresh.
Consider if Apple offer a 4k iMac, with keyboard and mouse, and potentially a 6 core desktop Intel CPU with a discrete GPU for $1099 later this year?
Even if Apple were still going cheap for the base model while retaining the 4k panel they'd be forced to use something like the i5-8259U at the very least to drive the display and that might not even meet their own minimum performance requirement.
Or they'd use an i5-8250U/i5-8265U and add a discrete GPU.
Either way, a $1099 machine with Thunderbolt 3, keyboard and mouse will be make the 2014 Mini look incredibly poor value.
When the middle SKU 2014 Mini sells for $699 but no keyboard, mouse, or 4k screen, and only 2 very old cores, even without looking at PC/Hackintosh options the iMac option begins to look incredibly attractive due to the 4k screen and CPU/GPU. And that's really going to get the goat of the folks would really need to use the Mini because they want to put something in a data centre with no screen.
Bear in mind that the 15" MacBook Pro never bothered with Iris Graphics after Haswell and went direct to discrete GPU and that Retina panel is has fewer pixels than 4k. I would say it only makes logical sense for the base iMac to go with discrete GPU and potentially equalise the range with the same desktop class CPU such as the i5-8400 at 2.8GHz.
The original 4k iMac had Broadwell Iris Pro graphics, and despite the fact that the following year Apple could have gone with the Iris Pro 580 from the Skylake CPU in 2017 they instead used the Radeon Pro 555 GPU - ostensibly the same GPU as in the 2016 MacBook Pro.
And if the iMac does go to 6 cores across the range then the Mini really has to go quad core thanks to available Intel options, potentially with discrete GPU as an option or on higher SKU because of users potentially using 4k screens now and in the future.
I notice Intel have launched a variant of the
i5-8305G with Vega WX M GL graphics (potentially a workstation part) which looks identical to the previously launched
RX version from much earlier this year. I can't see why Apple would use it as they have other options though and reviews from earlier in the year on the RX version of the CPU highlight increased heat, fan speed, and noise.
I expect the non-Retina 21.5" to be discontinued or to simply continue being sold as-is, without any sort of updates (like the 13" MacBook Air and nTB MBP are now). Apple is not going to care about Mojave's text rendering on this display and if they do they will simply put it out of its misery.
Apple is not going to reduce the cost of any model of the 4K 21.5" iMac, nor do I think they will offer anything different in the way of that base configuration. What I mean is that I believe is that the 2018 update will have the following at the $1299 price tag it currently sports:
* Core i5-8400 (replaces the Core i5-7400)
* 8GB DDR4-2666 (replaces DDR4-2400) configurable to 16GB
* 1TB 5400 RPM HDD (no change) configurable to 1TB Fusion, 256GB or 512GB SSD
* Radeon Pro 555x or radeon Pro 655 with 4GB of VRAM (replaces Radeon Pro 555 GPU and increases VRAM for Metal and Mojave)
* FaceTime HD camera (no change)
* 21.5" display, 4096x2304, 500 nits, Wide Color (P3)
* Stereo Speakers
* Microphone
* 3.5mm headphone jack
* SDXC card slot
* Four USB 3 ports
* Two Thunderbolt 3 ports
* 10/100/1000Base-T
* Wi-fi 802.11ac
* Bluetooth 5.0 (replaces Bluetooth 4.2)
Apple has been pushing prices higher as a matter of course and maintaining the base price for the 4K iMac at $1299 leaves some breathing room for them to increase the price of the Mac mini while offering a decent configuration at that $1099 price point.
Apple has an established precedent of using Intel's desktop CPUs in the iMac 4K and iMac 5K and I see no reason why they would want or need to use any of Intel's U-Series mobile CPUs (15w or 28w) beyond the base model 2017 21.5" iMac.
Whether by accident or design, the 21.5" 4K iMac is designed to look pretty attractive at $1299. Apples reckons the end-user will decide what they can live with in terms of DRAM and storage.
The 2014 Mac mini has been an incredibly poor value since, well, 2014, just ask anyone who has owned a Late 2012 Mac mini whether they would like to trade up, and chances are you will get a resounding NO from 99 out of 100 owners. The only thing the 2014 model has that the Late 2012 does not is a Thunderbolt 2 port. Everything else is just not all that compelling.
Apple went with discrete GPUs in the 2016" MacBook Pro because Intel really has no other customers for the Iris iGPU other than Apple and someone at Apple did the math. Price will ALWAYS win out over better technology with PC OEMs. Intel believes that its GT2 graphics are good enough for the vast majority of PC buyers today and began de-emphasizing work on GT3 and GT3e GPUs a while ago in favor of trying to compete with AMD and NVIDIA in the discrete GPU market (Arctic Sound).
Apple saw the writing on the wall and probably negotiated a price with AMD for the Radeon Pro GPUs at close to the same cost as the price differece between the Core i7-6700HQ (HD 530) and the Core i7-6770HQ (Iris Pro 580), which is $55 USD. I strongly suspect that AMD was willing to sell them the GPU for close to that price as the technology really is not that cutting edge, but it suited Apple's needs and gave both price tiers of the MacBook Pro a discrete GPU, which becomes a USP in their world. It also handed AMD another customer win for their portfolio.
Yes, the original 4K iMac had Iris Pro 6200 graphics, which did not go over very well when it was introduced. It was also a very inadequate solution for driving that particular 4K panel. Believe it or not, I do not think Apple will make that mistake again. Many would argue that the Radeon 555 is not all that much better than the Iris Pro 6200, but it is quite a bit more capable than the Iris Pro 6200 and the Iris Pro 580 (by a smaller margin) and way more capable than any Intel GT2 or GT3 part.
I do not think anyone is doubting that the Mac mini must go quad-core at this point. Intel has raised the core count (finally) and Apple either needs to kill the mini or update it to something that can actually compete.
Others on this forum has theorized that Apple may opt to use the Core i5-8305G and the Core i7-8706G with Radeon Pro WX Vega M GL graphics, but it will require a rethink on the chassis or an entirely new chassis to deal with the 65w TDP of those CPUs. It is possible, but it is a long shot for the current chassis.
Whatever happens, it should not be long now before we hear something.