We don't know how AMD 7nm will compare with Intel 10nm, it's not like AMD is releasing 7nm tomorrow, it's around 1H 2019 at this stage, so around 6 months before Intel releases 10nm and a new uarch, which will arrive in 2H 2019, assuming no more delays.
There are just so many unknowns, a lot of people think (or hope) Ryzen 2 aka 3000 series will have +15% IPC and 5GHz clocks. Of course we have nothing to back this up at this stage.
Quite frankly we don't even know if AMD Ryzen 3000 or whatever it's called will beat the 9900K, at least in terms of IPC and clocks. Of course if AMD increases the core count they can reclaim the MT performance crown even if they are still a bit behind in IPC and/or clockspeed