I'll continue to stand on my prediction that updated iMacs are coming as soon as a full set of Rx 6xx GPUs are available to provide the rumored "significant display performance upgrade." No clue if that will coincide with a redesign.
I don't think that will happen next month and don't believe Apple will release in December or January, so my expectations are for a February/March update. Maybe April since Apple updates are often slower than expected, but I bet we'll see new iMacs before WWDC.
If the new iMacs and Mac Pro are both ready in the same quarter then a combined event seems plausible.
That's my hunch as well; waiting for updated GPUs.
I don't keep tabs on Intel, but it seems the CPU candidates are set.
I highly doubt there will be a form factor redesign, and not because of the presence of the iMac Pro.
The 5K screen is one of the most expensive components of the iMac, and while I can see incremental improvements being made, a wholesale change requiring deeper design changes to it, as well as the casing is something Apple seems reluctant to invest in, as opposed to something like the shift with the X/XS, which was justifiable for the signature product and cash cow. Not a mature, and stagnant, if not shrinking product segment.
Apple has the flexibility to design the internal layout to suit whatever the component needs and performance targets are. The iMac's casing is nothing but a hollow shell with internal risers that can be placed where needed to mount the components, and with holes cut as needed.
A spec bump is predictable in all but a date that Apple is targeting.
The new mini is somewhat intriguing, and a return to the 2012 formula. If integrated graphics are sufficient for you, it can be an attractive alternative.
The interesting wildcard is the Mac Pro. What it will be, how it fits into the lineup, and how it might influence the rest, even though it will be a niche model.
In hindsight, the real bandits are the ones who bought the $4K iMac Pros during Microcenter's promotion.
