Comments from play testers and eSports figures suggest Valve may have an unexpected release up its sleeve.
According to a post on the ESEA forums, member Craig "Torbull" Levine is among a number of gamers asked to visit Valve and assist in testing a new Counter-strike game.
Levine posted a photo of himself at Valve, by the company's famous lobby decoration, as proof of his visit.
Similar stories have surfaced on the Steam forums, and have not been locked down by moderators.
ESL Pro manager Bastian Vieser also backs up the rumour:
"Just spend all day playing the new Counterstrike Global Offensive #CSGO at the #Valve HQ ! God I love my job.. oh and yeah... its that good!"
The eSports manager also checked in at Valve Software via Foursquare.
The most recent game in the Counter-strike series, an original Valve IP and one of the studio's key multiplayer franchises, is Counter-strike: Source, a remake of the first game rebuilt on the Source engine.
CS:S was first released in 2004 but has seen almost continuous development and support since its addition to the Steam catalogue. It is still considered one of the foremost PC multiplayer shooters.
Valve plays its in-development cards very close to the chest. Its only known project is fellow eSports candidate DOTA 2, soon to be debuted at gamescom next week.