This news comes courtesy of FanlessTech, which managed to pull down specs of the incoming NUC class. The top-of-the line offering will feature a quad-core (8-thread) Core i7-8559U and support for Intel Optane Memory. The mid-tier model features a Core i5-8259U (quad-core/8-threads) and an entry-level model with a Core i3-8109U processor.
All of the processors come with Iris Plus Graphics 655, clocked at 1.2GHz on the Core i7 and at 1.05GHz on the Core i3 and Core i5 SKUs. You'll also find 128MB of eDRAM, which serves as an L4 buffer for the L3 cache via the System Agent. The eDRAM is primarily used as a performance booster for the Iris Plus Graphics, but there are other benefits of the 50 GBps of bi-directional bandwidth (i.e. bypassing system DRAM).
Other features of note include Intel 300 Series chipset support, integrated Intel Wireless-AC (Gigabit-class), USB 3.1 Gen2 (10GB/s). Given that these are NUCs that are sold in a barebones configuration, you will have to supply your own memory and SSD/HDD for storage duties.