The next hero heading into the Heroes of the Storm Nexus is an unlikely one. Hailing from the Starcraft universe, "Probius" is, as the name implies, a literal probe. He is a ranged specialist that uses Pylons and Photon Cannons to take out enemies at range.
Probius is said to be heading to the PTR in the next few days.
In addition to the new hero, Blizzard also announced that several characters (Cho'Gall, Arthas, Anub'arak and Gazlowe) have some big changes incoming.
You can learn more about UI changes and incoming quality of life improvements by visiting the Heroes of the Storm site.