Give it a year for Sonys shareholders to pull their heads out of their asses and allow crossplay with the likes of Rocket League and Minecraft first, (Although the latter does require an Xbox Live account apparently, so I think Microsoft have really put that one down the ).
Then, once that happens, FDev can start considering enabling it for Elite. Right now, sure, Xbox and PC could probably do it. But then PS4 players have something of an inferior version of the game. Not exactly great PR to release a game then announce "Oh, hey guys, by the way we're upgrading everyone elses versions." Because believe me, that's how it would be seen by many.
The flip side, is that such a change would potentially expedite the 'Cranial-Posterior Extraction' of the aforementioned shareholders, OR it might make them burrow harder because "Mah muneez".
The long and short of it is simple:
Would it benefit the consumers? Yes, their games would become instantly more populated and many titles such as GTA, Elite or any game with an online multiplayer component could, and would, get a instant boost in longevity to lifespan before the servers go completely dead.
Would it benefit game developers? Yes for the same reason. More people playing their games means better prospect of investment for new titles and more prospective DLC buyers.
Would it benefit shareholders? I have no idea, but I don't give a stuff about them because they couldn't give less of a about me.
With cross-play, there's no reason to stick to one platform across the new-gen transitions. How many people stick to Xbox or PS because "Well, that's where my friends are so..."? I know I did. But with cross-play, there's only the exclusive IPs like Forza or Halo for Xbox, and Last of Us or Uncharted for Playstation to keep users attached to one platform.
