9900k is 8 core 16 thread, and insanely expensive.
A 12-core ryzen 2 with 15% IPC gain, at a cheaper price, with equivalent performance (as no doubt clocks will be lower than the 9900k) will be around equal in ST perf, and easily beat it in MT perf. It'll be a bloodbath in AMD's favour performance and value-wise.
But everyone will still buy Intel because mindshare and their logo is blue LOL.
EDIT: Gaming performance will still be a bit of a mystery due to ringbus vs. infinity fabric argument. Also, the IO die may present additional latency issues.