You'll never be able to cross play or cross host with the pc version you currently own (the steam one). When xbox gets cross play with pc it'll be with a new, different Win10 version that you'll download from the windows store.
And no, no pc and xbox fun time yet lol. And no entirely sure if we'll be able to host from our own pcs or only able to rent from 3rd party but think they did say something about hosting so fingers crossed!