One of the more interesting bits of Kingsman lore was established by Colin Firth's Harry Hart in 2014's Kingsman: The Secret Service, a bit of a description of the organization's history:
Since 1849, Kingsman tailors have clothed the world's most powerful individuals. By 1919, a great number of them had lost their heirs to World War I. That meant a lot of money, going un-inherited, and a lot of powerful men with the desire to preserve peace and protect life. Our founders realized that they could channel that wealth and influence for the greater good.
That premise was solid enough to warrant a film of it's own, and production is already under way for Kingsman: The Great Game, which will star Ralph Fiennes, Charles Dance, and Aaron Taylor Johnson. The film was originally slated to open in November of 2019, but has been pushed back to February 14th of 2020.
There was a lot of futile fanboy outrage over Taron Egerton's absence from the prequel movie, which four minutes of research would have alleviated – unless, of course, that outrage was over Eggsy not being present during the events of World War 1. (It's hard to say what fuels fanboy tears these days)
More details about Kingsman: The Great Game have been sparse, but we do know that the movie will focus on events leading up to the formation of the Kingsman organization after the obliteration of the younger ranks of English nobility in World War 1.
The setting should be ripe for an espionage thriller like Kingsman, with plenty of potential for bizarre gadgets, gas-masked bad guys, and aerial combat in bi-planes.
Director Matthew Vaughn has already discussed his plans for future Kingsman movies with the casts of the original two films:
The end of this movie [Golden Circle], if you think about it: you have Eggsy's definitely going to go on a new journey. Galahad, or Harry Hart's going on a new journey. Tequila's going on a new journey. Jeff's (Bridges) going on a new journey, Halle (Berry), the new agent Whiskey, is. The next movie is what happens to these characters. They're definitely not going to be doing what you've seen them do before.
It's highly probable that events from Kingsman: The Great Game will play into future installments of the modern-day Kingsman crew… we'll know for sure in early 2020.