I think microsoft will try to release it first in order to steal some market share(something like late 2019).
I really wish they all would wait until 2020 so we could have a nice upgrade for an affordable price.
With the way CPUs are improving in this last couple of years thanks to ryzen,by 2020 we could have a powerful ryzen APU(16 cores) + 16gb ram for $400-$500.