Bad news: there's been a leak that the next up-coming Intel Mac is going to use the Xeon W-3300 processor, which DOES NOT have big/little cores. This is rather disappointing as it would give us some hope for the next generation of processors and extend the usability of Mac OS:
I don't quite understand your reaction. These rumours have always been about an updated Mac Pro with Ice Lake Xeon. If you were expecting a consumer-grade processor, you were fooling yourself.
Now, a Mac Pro with a W-3365 would be a very slick machine (given XNU's limitation at 64 threads, the W-3375 makes little sense). Regardless whether anyone manages to hack a C621A platform, that would mean longer support for x86 by OS X, which would be good news for all of our present hacks.
But there's no reasonable hope of an updated consumer-grade Mac. The 10th generation on 400 series is what a hackintosh
user should target. Yes, that's already the previous generation but at least it has working iGPU and is well documented. Limitations begin with the 500 series. 600 series and later will be for dedicated hackers only to attempt—and may require hard work or not work at all as hackintoshes due to the different architecture.
Irrespective whether there is an Ice Lake Mac Pro, our x86 hacks are all bound to become living fossils, to loose feature parity with Apple Silicon and eventually turn into retrocomputing exercises—just like running MacOS on PowerPC or 68k (remember those?). An Ice Lake Mac Pro would only push slightly forward the end-of-useful-life date for our hacks but not avoid the unavoidable.
And, of course, Apple is still the same company which was happy to keep selling the MacPro 6,1 with the same IvyBridge-EP CPUs for most of the previous decade. The cylindrical design was very nice looking but was not suited to cool more powerful CPUs than what it was originally designed for. When Intel increased the TDP on the following generations of Xeon E5, Apple just sticked to its design for six years without bothering to update it for the new socket and processors. (It's actually amazing that Apple could source LGA2011 E5v2 long enough to keep selling its "trashcan" Mac Pro from 2019 until 2019, while Intel had released and then discontinued LGA2011-3 Haswell E5v3 and Broadwell E5v4 Xeons in between.)
The current tower design should certainly be able to accommodate upgraded cooling for W-3300 Xeons, but there is still no guarantee that Apple will bother releasing a new C621A motherboard for them rather than just keep selling the current W-3200 range until Apple Silicon can catch up with these.