The new Z390platform from Intel will bring support for the gen 9 mainstream CPUs that should go head to head with the Ryzen 2000 series. While the Z390 does not bring significant improvements, the i9-9900K is expected to deliver decent performance gains over the i7-8700K, also positioning itself as the direct competitor to AMD's Ryzen 7 2700 CPU.
https://www.notebookcheck.net/Intel-s-8-core-16-thread-mainstream-CPU-to-be-named-i9-9900K.313426.0.html
They're just adding a new tier to the mainline. Since the i5 and i7 are staying at 6 cores with/without HT, the i3 will remain a quad with no turbo on desktop as it has been since Coffee. It would have been clearer to portray this as Intel just adding an 8-core tier under the i9 name to their mainstream offerings and keep everything else categorized the same way.
I think the name i9 better reserved for HEDT class CPU or they better remove i3 and slap the price of the old i3 to the new i5. This isn't a wise move, clearly intel is panic due to recent competition and other unfortunate event surrounding them.