After spending quite a bit of time on the PTR it would appear that the Horizon Lunar Colony map is soon going to be ready for the live servers as well. According to the official Twitter the new map and its accompanying balance changes will be arriving on June 20th.
As for the balance changes, they are a bit... questionable. McCree and Reaper are getting some much needed buffs which is great, but Roadhog is getting reworked so heavily that both his functionality and playstyle are going to change drastically, and I'm not sure either of those is going to be for the better. You can find the full patch notes over at the Blizzard website, but for now here are all of the hero changes:
McCree
• Deadeye
- Targets now begin locking on after 0.2 seconds, instead of 0.8 seconds
- Damage accumulated over the first 1.0 seconds increased from 20 to 80 (damage per second after the first 1.0 seconds is unchanged)
Developer Comment: McCree’s ultimate can deal a lot of damage if it has a lot of time to build up, but it was often too difficult to get even a small amount of damage out before being stopped or killed. These changes make it more flexible and powerful.
Reaper
• The Reaping (Passive)
- Removed health orbs
- Now regains 20% of all damage done to heroes as health
Developer Comment: Reaper’s old healing passive was useful if you could kill a bunch of enemies in a row. But since enemies needed to be dead for it to work, it wasn’t very helpful unless the situation was already in your favor. His new passive lets him get immediate benefit from it, especially when fighting Tank heroes, which tend to be larger targets that deal lower damage.
Roadhog
• Head hitbox size reduced by 20%
• Scrap Gun
- Bullet damage decreased by 33%
- Fire rate increased by 30%
- Clip size increased from 4 to 5
Developer Comment: Roadhog’s head was abnormally large compared to similarly-sized characters, so we’re reducing its size to increase his survivability. The Scrap Gun changes reduce the power of his hook combo and alternate fire burst damage potential while still keeping his DPS roughly the same.
None of this is final, so until the patch arrives I would recommend taking these changes with a few grains of salt. And as a final note, here's a brief developer video going over their creation process and inspirations for the Horizon Lunar Colony map. Enjoy!