If you want to know how to transfer your Diablo 3 game from last-gen to next-gen systems when the Ultimate Evil Edition comes out, Blizzard has you covered.
Over on Battle.net, the written tutorial explains how to import your saves from Xbox 360 to Xbox One, and from PlayStation 3 to PS4.
It's simple, really: all you have to do is insert your Ultimate Evil Edition game into your brand spanking new system (or launch the digital version), and a prompt will ask if you want to import your save. This is if you have either a cloud save or local save.
If you are using online storage, be sure to download your saved data first.
As you already know, the kicker, is that this will work if you bought the game on Xbox 360 and want to transfer the save to PS4. Same with PS3 to Xbox One.
Obviously, this won't work with PC saves at all.
Blizzard calls this ability "cross-brand" and "cross-generational" transfer.
The steps you need to take are outlined through the link.
Diablo 3: Ultimate Evil Edition arrives on PS3, Xbox 360, PS4 and Xbox One on August 19.