In Reaper of Souls, paragon level system has been adjusted to a new one. Some changes were made to suit the expansion. Blizzard community manager began to answer players' questions at twitter, so here we just list some important pieces that most people may care about.
Legendary Items. Many of them were bound to the account in the new expansion. This doesn't mean the economic system and auction house become useless, but only some items need you to play to gain.
Beta Time. The exact time is not sure at the present. Mostly at later this year, maybe November or some other time. Before it, make sure your internet connection is continuous to have a wonderful Reaper of Souls journey.
Loot 2.0. Many new and revised system, including loot 2.0, are planed to released at the next patch, which is before the pre-sale of expansion. It's free to all players.
Paragon Points. This new feature has inspired many players' soul for diablo3. The paragon points is set to changeable but still under development. The final version is on the way. STC points can't be moved to HC, they are separate.
Nephalem Trials. It's absolutely random in the game, and appears as a portal. You don't know when it will come and what kind of monsters you'll meet. In fact, it's a sum of challenges that get harder and harder. The more monsters you kill in shorter time, the more Magnificent treasure chest you'll find.
Act V. Its length is the same as Act II. You need to defeat Diablo in Act IV to unlock Act V, and must install Reaper of Souls before playing.
More details will be announced as the GamsCom holding. Keep tuned for more information. Or go to diabloiiigold.com if you need to prepare enough cheap diablo 3 gold in stock before new game experience.