That's according to multiple sources! I guess when Greg Street was hired by Riot it was kind of a foregone conclusion. He was the lead communicator dude on WoW for a long time and left...quite a while ago to go to Riot. I guess that means that there's an MMO on the way!
While Street did not provide specifics, the MMO will take place in the world of Runeterra, the same universe that League of Legends and other Riot Games titles take place in. Street’s Twitter bio says that he oversees the League of Legends property, Riot Forge, and creative for Arcane, the League animated series. Street worked for Blizzard as a lead systems designer for World of Warcraft from 2008 until 2013, so he’s no newbie to the MMORPG scene.
I don't know what that means but I guess Riot has the money to make a big-time MMO. I don't particularly have any affinity for the LOL universe because I've never played LOL but hey, more competition in the MMO scene would be nice. Street left Blizzard almost 3 and a half years ago so this might be pretty far along in development?