Come to think of it, I'm waiting for the i3 6100 to come out and perhaps get the H170 motherboard which has the DDR3, wonder if DDR3 2133 or 2400 will matter or not. Or just go for the H170 with DD4 or Z170 instead, that way I have the option to move up to an i5 or i7 years later... but the problem is I'd have to get part by part separately due to lower income at the moment (laid off).
Keep in mind if Cannonlake ends up compatible with the 100 series you would need DDR4 anyway since it only has the DDR4 memory controller.