Can you play R6S with PC and PS4?
No.
No should come yet
Will that be supported at some point?
Unfortunately there's no crossplay for PC and Playstation players, so this is unfortunately not possible: 3
No, it can't be assumed. The game has been on the market for almost 6 years and so far Ubisoft hasn't shown any interest in it either. But it would of course not be feasible in practice. The console gamers would be at a disadvantage.