The cross-play discussion is one that just won't go away (until it arrives fully, presumably). Most recently it was with Fortnite, as the game playable across between Switch, PC and Xbox One players, while the PlayStation players are excluded, as Sony are reluctant to open up PlayStation Network. Indeed, even those who tried to access with their account on Fortnite from PlayStation 4 and later on any of the other platforms, found the account had been banned.
It's a complicated and slightly political situation, and more and more developers express an interest in opening things up. Now Bungie offers their opinion. More specifically, in a recent interview by Game Informer Bungie's Steve Cotton and Scott Taylor said they are interested in the possibility of introducing a multiplayer cross-platform functionality in Destiny 2, although they didn't have anything concrete to announce.
Would you like to play Destiny 2 with friends on other platforms?