The Xbox One and PlayStation 4 versions will have bigger worlds with large draw distances, almost all of the DLC and texture packs will be compatible with both versions, and will allow players to transfer their saved date from the PS3/Xbox 360/Vita versions to the next gen versions, but not be able to transfer them back.
Players who own the Xbox 360 and PS3 versions will be able to upgrade to the next gen versions for only $5, instead of paying $20. PS3 owners will be able to get the Vita version for free and vice versa via cross-buy. In addition, the PS3 and Vita versions will support cross saving between versions.
Unfortunately none of the next gen versions will support cross-play with the previous versions of Minecraft.
Minecraft on PlayStation 4, Xbox One, Vita, and Playstaiton 3 digitally sometime in August of this year.