Listings over at Geekbench database show several Kaby Lake desktop chips operating on an ASUS Z170-K motherboard. These chips include the Core i5-7400, Core i5-7500 and Core i5-7600K.
The motherboard is based on the 100-series chipset which gives us a hint that early samples are already compatible with existing motherboards. It’s up to Intel and their board partners to decide whether they would retain this compatibility down the road when Kaby Lake launches or limit it to the new 200-series boards. As of now, I have a feeling that 100-series and 200-series would allow compatibility with Kaby Lake chips but 200-series motherboards will have better I/O capabilities such as Optane SSD support.
Intel Kaby Lake Desktop Lineup:
***MSI Announces BIOS Updates for "Kaby Lake" 7th Gen. Core Processors[techpowerup]