In early access and beyond, if you log out in an expansion area, logging in with a 2.0 client will just throw an error and not let you in. One thing to note is that Collectors goodies are tied to your account so you only need to buy one Collectors Edition and the rest Standard Edition, but Early Access is tied to platform.
#Heavensward ps3 digital windows
So if you play on Windows and PS4, you will have to buy two copies of Heavensward-one for each platform. Just like 2.0, you only need one account, but each platform requires a seperate purchase.
#Heavensward ps3 digital upgrade
You cannot upgrade to Heavensward with a Windows package if your 2.0 client is from Steam, or vice versa. *Note the Steam version is the Windows version, but for reasons related to billing and other things we're not privy to they are treated as entirely seperate versions. Available physically or digitally for PS3, PS4, and Windows, and digital only for Steam and OSX. Note it also does not give access to the current game, as it won't release until the others do.
It will also not have early access (for reasons I'll explain later). This is the only version available for OSX, as the base game won't be available until Heavensward's launch.