I haven't seen any mention of the potential for cross-play for TGC 2 between Windows 10 PC's and Xbox Ones. I don't have enough of a feel for how current Windows 10 PC games interface with Xbox Ones to know if this will be doable, particularly if TGC 2 doesn't require Xbox Live Gold accounts for Xbox One players. Currently, I don't believe Windows 10 PC gamers have to have Xbox Live Gold accounts to engage in cross-play with Xbox One gamers. If I understand it correctly, Windows 10 PC gamers only have to have a Microsoft ID to do this.
Truth be known, I'd like to have Xbox Live Gold membership be a requirement for online multiplayer for the Xbox One version. The reason I selfishly say that is it seems that's what it will take to eliminate the communication lag between players trying to play the game concurrently in real time, without the 4 to 7 second lag between animation and voice. I know you can select 'quick animations' in the settings menu in the current game and get this delay down to about a second, but the abbreviated animations resulting from this make the multiplayer experience feel fractured, IMO.
Cross-play would be a real asset to Societies, one would imagine. It would be nice to have the diversity of two different platform bases playing in the same Society. It's probably a bit too soon to expect an official answer on this, but I'll go ahead and sow this seed for harvesting when it is ripe.