A post from Eurocom reveals this future Z390 chipset will deliver support for Intel's eight-core, sixteen-threaded processors. So next month six-core processors will enter Intel's mainstream lineup and sometime in the second half of 2018 you can expect two more cores added to the mix.
This eight-core chip from Intel will compete directly with AMD's currently available eight-core Ryzen 7 processors. Not a lot is known about these eight-core processors from Intel, it could be they're based on the 10nm Ice Lake architecture.
Anyway, the days of quad-core chips ruling the high-end market are quickly fading.