JustinThyme wrote:
While I would agree there can be no 100% guaranteed answer my guess would be not even remotely. the Z170 doesnt even fully support kaby lake then add to it we are going to 6 cores over 4 cores and a Z300 series chipset is part of the package aimed for launch at the same time. If I was a betting man I would place my money that the pins are changing and so are the boards and a Z270 wont even support it. This is of course all speculation.

Sure pure speculation.....but Coffee Lake is the same socket 1151 as Kaby lake and Sky Lake (so far nothing else have been reported) . So when we go deeper in you will notice that the 1151 stands for how many pins on the CPU. So when Coffe Lake uses tthe same numbers (1151 pins) Coffe Lake will fit just fine on Z170 (Z270) boards. As you recall The Z170 boards had a BIOS Update to FULL support of Kaby Lake.....not 90 % but 100%. It was the BIOS 3101 that kicked in Kaby Lake support. If you still have the Sky Lake on Z170 no need to go further than BIOS 2202. Conclusion must be that YES you can use Coffee Lake CPU on Z170 (Z270) boards.....BUT with 6 cores on Coffee you WILL miss 2 cores on Skylake and Kaby boards. But how much it will affect performance is unknown. I do not think you will notice anything. Only in Benchmarks and playing games on highest settings on 4K. And i don't think it will be something you will notice when playing games. A couple of more framerates maybe 5. The real difference will be in PCIe lanes. Coffe Lake will have 44.

Leaked SiSoftware Sandra screens have been posted showing a 6-core Coffee Lake CPU running on the Z270 chipset. These are probably engineering samples but this shows that technically it is possible.

I hope that Intel do permit support for these CPUs on Z270 and Z170 as this will provide an easy upgrade for many. If a new board is required, then switching to Ryzen may be a more attractive option.