I'm going to boldly come out and predict it will. I know some of you will say, "Put down the crack pipe, that's years away still".
But let's look at precedent. They came out with the 5K iMac earlier than most thought too. Also, not long before, Dell had released a 5K standalone monitor. Dell has released a standalone 8K monitor. A clear harbinger of an 8K iMac if past is prologue!
Or not.
Apple prioritizes DPI for their desktops and laptops, which is ~110DPI for non-Retina and ~220DPI for Retina. You can try it for yourself at
https://www.sven.de/dpi/
iMac/iMac 5K
iMac 5K - 5280x2880 @ 27" = 217.57 DPI
iMac - 2560x1440 @27" = 108.79 DPI
iMac 4K
4096x2304 @21.5" = 218.58 DPI
2048x1152 @21.5" = 109.29 DPI - @2x resolution, but DPI shown is non-Retina; I have a Dell monitor that does this resolution natively.
iMac (non-Retina)
1920X1080 @21.5" = 102.46 DPI; outside spec a bit and it rears its ugly head sometimes.
15" Retina MacBook Pro
2880x1880 = 220.53 DPI
15" NON Retina MacBook Pro
1140x900 = 110.27
So, a pure 8K display would be need to be 40"
7680x4320@40" = 220.29 DPI or 3840X2160@2x for Retina Display.
And an (Apple) 8K DCI display would need to be 42 or 43"(which is exactly twice the size as the 4K iMac)
8192x4320@42" = 220.51 DPI or 4096x2160@2x for a Retina Display. However, the aspect ratio becomes 17:9
8192x4608@43" = 218.58 DPI or 4096x2304@2x for a Retina Display. Aspect ration remains 16:9
I can see 40" and 43" as standalone Apple Cinema Displays, but I cannot see them being used for an iMac display unless Apple decides that Retina is more than ~220DPI, which I suppose they could decide to do at some point in the future.