Based on well-known Samsung B-Die DDR4 ICs, new G.Skill memory kits will include the 16GB (2x8GB) Trident Z 4600MHz CL19-25-25-45 kit running at 1.5V as well as the 32GB (4x8GB) Trident Z 4200MHz kit running at 1.4V. G.Skill already ran the validation test on Asus ROG Maximus X Apex motherboard and Intel's latest Core i5-8600K CPU.
As you can see from the table below, the Trident Z kits will be available in 16GB and 32GB kits, with various frequencies ranging from 4000MHz to 4600MHz.
In addition to a couple of Trident Z kits, G.Skill also introduced two new Trident Z RGB kits, the 32GB (4x8GB) DDR4-4000 CL18-19-19-39 and the 64GB (4x16GB) DDR4-3733 CL17-19-19-39 kit, both running at 1.35V.
According to G.Skill, all these kits will be available in November 2017.