We'll have to see what Blizzard has planned, but if members of the Overwatch team are headed to Luna in order to unearth the truth, it's looking likely that it will form the basis of a new map, perhaps leading to the discovery that Hammond is now its leader. My suspicion is that we'll be getting a new Horizon Lunar Colony map soon.
Blizzard is teasing some lore for Overwatch, which some believe could point to new content. It sheds light on the program taking place in Horizon Lunar Colony. Hammond is a younger gorilla, and he's apparently the only specimen from the Lunar Colony that is unaccounted for, other than Winston of course. Given Hammond is also mentioned by name in the email exchanges it seems obvious that he is a big part of the reveal.
Lucheng Interstellar has released the first image of the Horizon Lunar Colony's monitoring systems, showing that seven specimens are still alive and well in the facility, along with several scientists, through a lot of them are huddled close to each other. The gorillas launched an uprising, killing all the scientists and claiming the moon-base for their own. Hammond is mentioned previously in the messages offered as having been missing for a week, and he's described as a "smaller test subject". Using a rocket ship, Winston escaped to Earth and joined Overwatch. During a livestream on Twitch, Kaplan said "there's also some really cool hero news just on the horizon", which is either a fun coincidence or a very sneaky tease about the origins of Overwatch's next character.