It's very rare for an upstart game company to hit it big on their very first title, but that is exactly what happened to Riot Games with League of Legends back in 2009. Riot's co-founders, Brandon “Ryze” Beck and Marc “Tryndamere” Merrill announced in an all-new blog post that they would be stepping away from their management roles within the company to re-focus their efforts on "finally put[ting] the “s” in Riot Games."
As noted in the announcement, management duties will now fall to Dylan Jadeja (CFO), Scott Gelb (CTO), and Nicolo Laurent (President) who are all described as "longtime Rioters."
Tryndamere and Ryze didn't give any indication on what kind of game they will be working on next, though fans over on NeoGAF seem to think that it'll be a Battle Royale. Given the vastly growing popularity of the genre, it wouldn't be surprising to see Riot go from one hot genre to another.
Whatever it is they'll make, we'll be very interested in seeing what the studio comes up with.
[Riot Games, NeoGAF]