Valorant is one of many new projects set to assure the "Games" part of Riot Games reads true. And while it was part of a massive rollout of announcements, the truth seems to be that Valorant has been in development for a long time up to this point.
In a Discord AMA with Trevor "Classick" Romleski, lead game designer, on the official Valorant Discord (transcribed here by Reddit user "thepixelbuster"), the project has been in development for quite some time. In response to how long ago he started working on Valorant, he responded with about six years in total; "three years R&D, three years pre-production/production." In a Polygon feature on Valorant's development, other developers give a similar timeframe of "just over six years."
Other parts of the AMA point to where Valorant will differ from Riot Games' well-known property, League of Legends. Romleski says Valorant is a "different IP" from League, so we probably won't see Teemo picking up a rifle anytime soon.
There are also a lot of customization options, like setting your crosshair shapes and colorblind options that are currently in progress. Though Romleski says there's "no singleplayer [sic]," the team is interested in "further agent development through other methods over time."
Valorant looks like Riot Games' take on the Counter-Strike genre, complete with ancient hardware compatibility, in-game economy, and objective-oriented gameplay. It's already received some notable praise from Counter-Strike players, and is set to launch in summer 2020.
It's also one of several new projects in the works at Riot Games, including a fighting game and Legends of Runeterra, which is currently in open beta.