Forever changes
Energy regenerates continuously; combo points persist on original target when switching (games.gg); Mutilate, Venom (Assassination); Restless Blades, Hack and Slash, Puncturing Wounds (Combat); Hemorrhage rework, Thousand Cuts, Cutthroat, Quietus (Subtlety).
Confidence note
Reported (single credible outlet, BlizzCon demo build; subject to beta change)