Bungie has confirmed that cross save support will arrive on August 21st to Destiny 2.
This will enable gamers to transport their Guardians to the platform of their choice including PC, PS4 or Xbox One.
The will not allow gamers to play with their friends on different platforms, so let that me noted it is not cross play.
Any Silver that you have accrued is also tied to that specific platform where you earned it, so no transfers on that either.