Path of Exile’s 3.9.0 expansion highlights have been outlines by the team in a recent forum post.
The upcoming expansion will feature a “good balance of risk vs reward” as well as compelling endgame, according the post. New item rewards are in store as well, in addition to balance.
“We're also focusing some balance attention on bows, though this revamp isn't of the same scale as our spellcasting and melee changes earlier this year. The expansion also includes all the usual divination cards, unique items, new skills and so on that you're used to from Path of Exile releases.”