PC Gamer spoke with Blizzard at Gamescom, learning that a version 2.0 patch for Diablo III is planned for release around the same time as the newly revealed Reaper of Souls expansion for the action/RPG sequel. Here's the explanation of what's in the patch versus what's only found in the expansion:

Lead content designer Kevin Martens ran us through the free features of patch 2.0. “You’re going to get all the loot, you’re going to get all the new item types, you’re going to get all the new legendary affixes, you’re going to get our new gem type – which is the diamond – and you’re going to get all the changes to the rules, the smart drop system, the targeted drop system, probably you’ll get loot runs – we haven’t figured that one out yet – probably you’ll get paragon, etc, etc.”

Martens explains the division as being between systemic changes to the game’s rules and new content that the player to discover. “All the content is Reaper of Souls, like the act five stuff and the new higher level items, from sixty to seventy – so that level cap increase, which includes the new abilities, the new runes and the new passives for existing classes.”